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/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
* Copyright (c) 2016 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/bpf.h>
#include <linux/bpf_verifier.h>
#include <linux/filter.h>
#include <net/netlink.h>
#include <linux/file.h>
#include <linux/vmalloc.h>
#include <linux/stringify.h>
/* bpf_check() is a static code analyzer that walks eBPF program
* instruction by instruction and updates register/stack state.
* All paths of conditional branches are analyzed until 'bpf_exit' insn.
*
* The first pass is depth-first-search to check that the program is a DAG.
* It rejects the following programs:
* - larger than BPF_MAXINSNS insns
* - if loop is present (detected via back-edge)
* - unreachable insns exist (shouldn't be a forest. program = one function)
* - out of bounds or malformed jumps
* The second pass is all possible path descent from the 1st insn.
* Since it's analyzing all pathes through the program, the length of the
* analysis is limited to 64k insn, which may be hit even if total number of
* insn is less then 4K, but there are too many branches that change stack/regs.
* Number of 'branches to be analyzed' is limited to 1k
*
* On entry to each instruction, each register has a type, and the instruction
* changes the types of the registers depending on instruction semantics.
* If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
* copied to R1.
*
* All registers are 64-bit.
* R0 - return register
* R1-R5 argument passing registers
* R6-R9 callee saved registers
* R10 - frame pointer read-only
*
* At the start of BPF program the register R1 contains a pointer to bpf_context
* and has type PTR_TO_CTX.
*
* Verifier tracks arithmetic operations on pointers in case:
* BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
* BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
* 1st insn copies R10 (which has FRAME_PTR) type into R1
* and 2nd arithmetic instruction is pattern matched to recognize
* that it wants to construct a pointer to some element within stack.
* So after 2nd insn, the register R1 has type PTR_TO_STACK
* (and -20 constant is saved for further stack bounds checking).
* Meaning that this reg is a pointer to stack plus known immediate constant.
*
* Most of the time the registers have SCALAR_VALUE type, which
* means the register has some value, but it's not a valid pointer.
* (like pointer plus pointer becomes SCALAR_VALUE type)
*
* When verifier sees load or store instructions the type of base register
* can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, PTR_TO_STACK. These are three pointer
* types recognized by check_mem_access() function.
*
* PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
* and the range of [ptr, ptr + map's value_size) is accessible.
*
* registers used to pass values to function calls are checked against
* function argument constraints.
*
* ARG_PTR_TO_MAP_KEY is one of such argument constraints.
* It means that the register type passed to this function must be
* PTR_TO_STACK and it will be used inside the function as
* 'pointer to map element key'
*
* For example the argument constraints for bpf_map_lookup_elem():
* .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
* .arg1_type = ARG_CONST_MAP_PTR,
* .arg2_type = ARG_PTR_TO_MAP_KEY,
*
* ret_type says that this function returns 'pointer to map elem value or null'
* function expects 1st argument to be a const pointer to 'struct bpf_map' and
* 2nd argument should be a pointer to stack, which will be used inside
* the helper function as a pointer to map element key.
*
* On the kernel side the helper function looks like:
* u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
* {
* struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
* void *key = (void *) (unsigned long) r2;
* void *value;
*
* here kernel can access 'key' and 'map' pointers safely, knowing that
* [key, key + map->key_size) bytes are valid and were initialized on
* the stack of eBPF program.
* }
*
* Corresponding eBPF program may look like:
* BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR
* BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
* BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP
* BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
* here verifier looks at prototype of map_lookup_elem() and sees:
* .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
* Now verifier knows that this map has key of R1->map_ptr->key_size bytes
*
* Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
* Now verifier checks that [R2, R2 + map's key_size) are within stack limits
* and were initialized prior to this call.
* If it's ok, then verifier allows this BPF_CALL insn and looks at
* .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
* R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
* returns ether pointer to map value or NULL.
*
* When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
* insn, the register holding that pointer in the true branch changes state to
* PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
* branch. See check_cond_jmp_op().
*
* After the call R0 is set to return type of the function and registers R1-R5
* are set to NOT_INIT to indicate that they are no longer readable.
*/
/* verifier_state + insn_idx are pushed to stack when branch is encountered */
struct bpf_verifier_stack_elem {
/* verifer state is 'st'
* before processing instruction 'insn_idx'
* and after processing instruction 'prev_insn_idx'
*/
struct bpf_verifier_state st;
int insn_idx;
int prev_insn_idx;
struct bpf_verifier_stack_elem *next;
};
#define BPF_COMPLEXITY_LIMIT_INSNS 131072
#define BPF_COMPLEXITY_LIMIT_STACK 1024
#define BPF_MAP_PTR_POISON ((void *)0xeB9F + POISON_POINTER_DELTA)
struct bpf_call_arg_meta {
struct bpf_map *map_ptr;
bool raw_mode;
bool pkt_access;
int regno;
int access_size;
};
/* verbose verifier prints what it's seeing
* bpf_check() is called under lock, so no race to access these global vars
*/
static u32 log_level, log_size, log_len;
static char *log_buf;
static DEFINE_MUTEX(bpf_verifier_lock);
/* log_level controls verbosity level of eBPF verifier.
* verbose() is used to dump the verification trace to the log, so the user
* can figure out what's wrong with the program
*/
static __printf(1, 2) void verbose(const char *fmt, ...)
{
va_list args;
if (log_level == 0 || log_len >= log_size - 1)
return;
va_start(args, fmt);
log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
va_end(args);
}
/* string representation of 'enum bpf_reg_type' */
static const char * const reg_type_str[] = {
[NOT_INIT] = "?",
[SCALAR_VALUE] = "inv",
[PTR_TO_CTX] = "ctx",
[CONST_PTR_TO_MAP] = "map_ptr",
[PTR_TO_MAP_VALUE] = "map_value",
[PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
[PTR_TO_STACK] = "fp",
[PTR_TO_PACKET] = "pkt",
[PTR_TO_PACKET_END] = "pkt_end",
};
#define __BPF_FUNC_STR_FN(x) [BPF_FUNC_ ## x] = __stringify(bpf_ ## x)
static const char * const func_id_str[] = {
__BPF_FUNC_MAPPER(__BPF_FUNC_STR_FN)
};
#undef __BPF_FUNC_STR_FN
static const char *func_id_name(int id)
{
BUILD_BUG_ON(ARRAY_SIZE(func_id_str) != __BPF_FUNC_MAX_ID);
if (id >= 0 && id < __BPF_FUNC_MAX_ID && func_id_str[id])
return func_id_str[id];
else
return "unknown";
}
static void print_verifier_state(struct bpf_verifier_state *state)
{
struct bpf_reg_state *reg;
enum bpf_reg_type t;
int i;
for (i = 0; i < MAX_BPF_REG; i++) {
reg = &state->regs[i];
t = reg->type;
if (t == NOT_INIT)
continue;
verbose(" R%d=%s", i, reg_type_str[t]);
if ((t == SCALAR_VALUE || t == PTR_TO_STACK) &&
tnum_is_const(reg->var_off)) {
/* reg->off should be 0 for SCALAR_VALUE */
verbose("%lld", reg->var_off.value + reg->off);
} else {
verbose("(id=%d", reg->id);
if (t != SCALAR_VALUE)
verbose(",off=%d", reg->off);
if (t == PTR_TO_PACKET)
verbose(",r=%d", reg->range);
else if (t == CONST_PTR_TO_MAP ||
t == PTR_TO_MAP_VALUE ||
t == PTR_TO_MAP_VALUE_OR_NULL)
verbose(",ks=%d,vs=%d",
reg->map_ptr->key_size,
reg->map_ptr->value_size);
if (tnum_is_const(reg->var_off)) {
/* Typically an immediate SCALAR_VALUE, but
* could be a pointer whose offset is too big
* for reg->off
*/
verbose(",imm=%llx", reg->var_off.value);
} else {
if (reg->smin_value != reg->umin_value &&
reg->smin_value != S64_MIN)
verbose(",smin_value=%lld",
(long long)reg->smin_value);
if (reg->smax_value != reg->umax_value &&
reg->smax_value != S64_MAX)
verbose(",smax_value=%lld",
(long long)reg->smax_value);
if (reg->umin_value != 0)
verbose(",umin_value=%llu",
(unsigned long long)reg->umin_value);
if (reg->umax_value != U64_MAX)
verbose(",umax_value=%llu",
(unsigned long long)reg->umax_value);
if (!tnum_is_unknown(reg->var_off)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(",var_off=%s", tn_buf);
}
}
verbose(")");
}
}
for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
if (state->stack_slot_type[i] == STACK_SPILL)
verbose(" fp%d=%s", -MAX_BPF_STACK + i,
reg_type_str[state->spilled_regs[i / BPF_REG_SIZE].type]);
}
verbose("\n");
}
static const char *const bpf_class_string[] = {
[BPF_LD] = "ld",
[BPF_LDX] = "ldx",
[BPF_ST] = "st",
[BPF_STX] = "stx",
[BPF_ALU] = "alu",
[BPF_JMP] = "jmp",
[BPF_RET] = "BUG",
[BPF_ALU64] = "alu64",
};
static const char *const bpf_alu_string[16] = {
[BPF_ADD >> 4] = "+=",
[BPF_SUB >> 4] = "-=",
[BPF_MUL >> 4] = "*=",
[BPF_DIV >> 4] = "/=",
[BPF_OR >> 4] = "|=",
[BPF_AND >> 4] = "&=",
[BPF_LSH >> 4] = "<<=",
[BPF_RSH >> 4] = ">>=",
[BPF_NEG >> 4] = "neg",
[BPF_MOD >> 4] = "%=",
[BPF_XOR >> 4] = "^=",
[BPF_MOV >> 4] = "=",
[BPF_ARSH >> 4] = "s>>=",
[BPF_END >> 4] = "endian",
};
static const char *const bpf_ldst_string[] = {
[BPF_W >> 3] = "u32",
[BPF_H >> 3] = "u16",
[BPF_B >> 3] = "u8",
[BPF_DW >> 3] = "u64",
};
static const char *const bpf_jmp_string[16] = {
[BPF_JA >> 4] = "jmp",
[BPF_JEQ >> 4] = "==",
[BPF_JGT >> 4] = ">",
[BPF_JLT >> 4] = "<",
[BPF_JGE >> 4] = ">=",
[BPF_JLE >> 4] = "<=",
[BPF_JSET >> 4] = "&",
[BPF_JNE >> 4] = "!=",
[BPF_JSGT >> 4] = "s>",
[BPF_JSLT >> 4] = "s<",
[BPF_JSGE >> 4] = "s>=",
[BPF_JSLE >> 4] = "s<=",
[BPF_CALL >> 4] = "call",
[BPF_EXIT >> 4] = "exit",
};
static void print_bpf_insn(const struct bpf_verifier_env *env,
const struct bpf_insn *insn)
{
u8 class = BPF_CLASS(insn->code);
if (class == BPF_ALU || class == BPF_ALU64) {
if (BPF_SRC(insn->code) == BPF_X)
verbose("(%02x) %sr%d %s %sr%d\n",
insn->code, class == BPF_ALU ? "(u32) " : "",
insn->dst_reg,
bpf_alu_string[BPF_OP(insn->code) >> 4],
class == BPF_ALU ? "(u32) " : "",
insn->src_reg);
else
verbose("(%02x) %sr%d %s %s%d\n",
insn->code, class == BPF_ALU ? "(u32) " : "",
insn->dst_reg,
bpf_alu_string[BPF_OP(insn->code) >> 4],
class == BPF_ALU ? "(u32) " : "",
insn->imm);
} else if (class == BPF_STX) {
if (BPF_MODE(insn->code) == BPF_MEM)
verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg,
insn->off, insn->src_reg);
else if (BPF_MODE(insn->code) == BPF_XADD)
verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg, insn->off,
insn->src_reg);
else
verbose("BUG_%02x\n", insn->code);
} else if (class == BPF_ST) {
if (BPF_MODE(insn->code) != BPF_MEM) {
verbose("BUG_st_%02x\n", insn->code);
return;
}
verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg,
insn->off, insn->imm);
} else if (class == BPF_LDX) {
if (BPF_MODE(insn->code) != BPF_MEM) {
verbose("BUG_ldx_%02x\n", insn->code);
return;
}
verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
insn->code, insn->dst_reg,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->src_reg, insn->off);
} else if (class == BPF_LD) {
if (BPF_MODE(insn->code) == BPF_ABS) {
verbose("(%02x) r0 = *(%s *)skb[%d]\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->imm);
} else if (BPF_MODE(insn->code) == BPF_IND) {
verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->src_reg, insn->imm);
} else if (BPF_MODE(insn->code) == BPF_IMM &&
BPF_SIZE(insn->code) == BPF_DW) {
/* At this point, we already made sure that the second
* part of the ldimm64 insn is accessible.
*/
u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
bool map_ptr = insn->src_reg == BPF_PSEUDO_MAP_FD;
if (map_ptr && !env->allow_ptr_leaks)
imm = 0;
verbose("(%02x) r%d = 0x%llx\n", insn->code,
insn->dst_reg, (unsigned long long)imm);
} else {
verbose("BUG_ld_%02x\n", insn->code);
return;
}
} else if (class == BPF_JMP) {
u8 opcode = BPF_OP(insn->code);
if (opcode == BPF_CALL) {
verbose("(%02x) call %s#%d\n", insn->code,
func_id_name(insn->imm), insn->imm);
} else if (insn->code == (BPF_JMP | BPF_JA)) {
verbose("(%02x) goto pc%+d\n",
insn->code, insn->off);
} else if (insn->code == (BPF_JMP | BPF_EXIT)) {
verbose("(%02x) exit\n", insn->code);
} else if (BPF_SRC(insn->code) == BPF_X) {
verbose("(%02x) if r%d %s r%d goto pc%+d\n",
insn->code, insn->dst_reg,
bpf_jmp_string[BPF_OP(insn->code) >> 4],
insn->src_reg, insn->off);
} else {
verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
insn->code, insn->dst_reg,
bpf_jmp_string[BPF_OP(insn->code) >> 4],
insn->imm, insn->off);
}
} else {
verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
}
}
static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx)
{
struct bpf_verifier_stack_elem *elem;
int insn_idx;
if (env->head == NULL)
return -1;
memcpy(&env->cur_state, &env->head->st, sizeof(env->cur_state));
insn_idx = env->head->insn_idx;
if (prev_insn_idx)
*prev_insn_idx = env->head->prev_insn_idx;
elem = env->head->next;
kfree(env->head);
env->head = elem;
env->stack_size--;
return insn_idx;
}
static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
int insn_idx, int prev_insn_idx)
{
struct bpf_verifier_stack_elem *elem;
elem = kmalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL);
if (!elem)
goto err;
memcpy(&elem->st, &env->cur_state, sizeof(env->cur_state));
elem->insn_idx = insn_idx;
elem->prev_insn_idx = prev_insn_idx;
elem->next = env->head;
env->head = elem;
env->stack_size++;
if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) {
verbose("BPF program is too complex\n");
goto err;
}
return &elem->st;
err:
/* pop all elements and return */
while (pop_stack(env, NULL) >= 0);
return NULL;
}
#define CALLER_SAVED_REGS 6
static const int caller_saved[CALLER_SAVED_REGS] = {
BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
};
static void __mark_reg_not_init(struct bpf_reg_state *reg);
/* Mark the unknown part of a register (variable offset or scalar value) as
* known to have the value @imm.
*/
static void __mark_reg_known(struct bpf_reg_state *reg, u64 imm)
{
reg->id = 0;
reg->var_off = tnum_const(imm);
reg->smin_value = (s64)imm;
reg->smax_value = (s64)imm;
reg->umin_value = imm;
reg->umax_value = imm;
}
/* Mark the 'variable offset' part of a register as zero. This should be
* used only on registers holding a pointer type.
*/
static void __mark_reg_known_zero(struct bpf_reg_state *reg)
{
__mark_reg_known(reg, 0);
}
static void mark_reg_known_zero(struct bpf_reg_state *regs, u32 regno)
{
if (WARN_ON(regno >= MAX_BPF_REG)) {
verbose("mark_reg_known_zero(regs, %u)\n", regno);
/* Something bad happened, let's kill all regs */
for (regno = 0; regno < MAX_BPF_REG; regno++)
__mark_reg_not_init(regs + regno);
return;
}
__mark_reg_known_zero(regs + regno);
}
/* Attempts to improve min/max values based on var_off information */
static void __update_reg_bounds(struct bpf_reg_state *reg)
{
/* min signed is max(sign bit) | min(other bits) */
reg->smin_value = max_t(s64, reg->smin_value,
reg->var_off.value | (reg->var_off.mask & S64_MIN));
/* max signed is min(sign bit) | max(other bits) */
reg->smax_value = min_t(s64, reg->smax_value,
reg->var_off.value | (reg->var_off.mask & S64_MAX));
reg->umin_value = max(reg->umin_value, reg->var_off.value);
reg->umax_value = min(reg->umax_value,
reg->var_off.value | reg->var_off.mask);
}
/* Uses signed min/max values to inform unsigned, and vice-versa */
static void __reg_deduce_bounds(struct bpf_reg_state *reg)
{
/* Learn sign from signed bounds.
* If we cannot cross the sign boundary, then signed and unsigned bounds
* are the same, so combine. This works even in the negative case, e.g.
* -3 s<= x s<= -1 implies 0xf...fd u<= x u<= 0xf...ff.
*/
if (reg->smin_value >= 0 || reg->smax_value < 0) {
reg->smin_value = reg->umin_value = max_t(u64, reg->smin_value,
reg->umin_value);
reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value,
reg->umax_value);
return;
}
/* Learn sign from unsigned bounds. Signed bounds cross the sign
* boundary, so we must be careful.
*/
if ((s64)reg->umax_value >= 0) {
/* Positive. We can't learn anything from the smin, but smax
* is positive, hence safe.
*/
reg->smin_value = reg->umin_value;
reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value,
reg->umax_value);
} else if ((s64)reg->umin_value < 0) {
/* Negative. We can't learn anything from the smax, but smin
* is negative, hence safe.
*/
reg->smin_value = reg->umin_value = max_t(u64, reg->smin_value,
reg->umin_value);
reg->smax_value = reg->umax_value;
}
}
/* Attempts to improve var_off based on unsigned min/max information */
static void __reg_bound_offset(struct bpf_reg_state *reg)
{
reg->var_off = tnum_intersect(reg->var_off,
tnum_range(reg->umin_value,
reg->umax_value));
}
/* Reset the min/max bounds of a register */
static void __mark_reg_unbounded(struct bpf_reg_state *reg)
{
reg->smin_value = S64_MIN;
reg->smax_value = S64_MAX;
reg->umin_value = 0;
reg->umax_value = U64_MAX;
}
/* Mark a register as having a completely unknown (scalar) value. */
static void __mark_reg_unknown(struct bpf_reg_state *reg)
{
reg->type = SCALAR_VALUE;
reg->id = 0;
reg->off = 0;
reg->var_off = tnum_unknown;
__mark_reg_unbounded(reg);
}
static void mark_reg_unknown(struct bpf_reg_state *regs, u32 regno)
{
if (WARN_ON(regno >= MAX_BPF_REG)) {
verbose("mark_reg_unknown(regs, %u)\n", regno);
/* Something bad happened, let's kill all regs */
for (regno = 0; regno < MAX_BPF_REG; regno++)
__mark_reg_not_init(regs + regno);
return;
}
__mark_reg_unknown(regs + regno);
}
static void __mark_reg_not_init(struct bpf_reg_state *reg)
{
__mark_reg_unknown(reg);
reg->type = NOT_INIT;
}
static void mark_reg_not_init(struct bpf_reg_state *regs, u32 regno)
{
if (WARN_ON(regno >= MAX_BPF_REG)) {
verbose("mark_reg_not_init(regs, %u)\n", regno);
/* Something bad happened, let's kill all regs */
for (regno = 0; regno < MAX_BPF_REG; regno++)
__mark_reg_not_init(regs + regno);
return;
}
__mark_reg_not_init(regs + regno);
}
static void init_reg_state(struct bpf_reg_state *regs)
{
int i;
for (i = 0; i < MAX_BPF_REG; i++) {
mark_reg_not_init(regs, i);
regs[i].live = REG_LIVE_NONE;
}
/* frame pointer */
regs[BPF_REG_FP].type = PTR_TO_STACK;
mark_reg_known_zero(regs, BPF_REG_FP);
/* 1st arg to a function */
regs[BPF_REG_1].type = PTR_TO_CTX;
mark_reg_known_zero(regs, BPF_REG_1);
}
enum reg_arg_type {
SRC_OP, /* register is used as source operand */
DST_OP, /* register is used as destination operand */
DST_OP_NO_MARK /* same as above, check only, don't mark */
};
static void mark_reg_read(const struct bpf_verifier_state *state, u32 regno)
{
struct bpf_verifier_state *parent = state->parent;
if (regno == BPF_REG_FP)
/* We don't need to worry about FP liveness because it's read-only */
return;
while (parent) {
/* if read wasn't screened by an earlier write ... */
if (state->regs[regno].live & REG_LIVE_WRITTEN)
break;
/* ... then we depend on parent's value */
parent->regs[regno].live |= REG_LIVE_READ;
state = parent;
parent = state->parent;
}
}
static int check_reg_arg(struct bpf_verifier_env *env, u32 regno,
enum reg_arg_type t)
{
struct bpf_reg_state *regs = env->cur_state.regs;
if (regno >= MAX_BPF_REG) {
verbose("R%d is invalid\n", regno);
return -EINVAL;
}
if (t == SRC_OP) {
/* check whether register used as source operand can be read */
if (regs[regno].type == NOT_INIT) {
verbose("R%d !read_ok\n", regno);
return -EACCES;
}
mark_reg_read(&env->cur_state, regno);
} else {
/* check whether register used as dest operand can be written to */
if (regno == BPF_REG_FP) {
verbose("frame pointer is read only\n");
return -EACCES;
}
regs[regno].live |= REG_LIVE_WRITTEN;
if (t == DST_OP)
mark_reg_unknown(regs, regno);
}
return 0;
}
static bool is_spillable_regtype(enum bpf_reg_type type)
{
switch (type) {
case PTR_TO_MAP_VALUE:
case PTR_TO_MAP_VALUE_OR_NULL:
case PTR_TO_STACK:
case PTR_TO_CTX:
case PTR_TO_PACKET:
case PTR_TO_PACKET_END:
case CONST_PTR_TO_MAP:
return true;
default:
return false;
}
}
/* check_stack_read/write functions track spill/fill of registers,
* stack boundary and alignment are checked in check_mem_access()
*/
static int check_stack_write(struct bpf_verifier_state *state, int off,
int size, int value_regno)
{
int i, spi = (MAX_BPF_STACK + off) / BPF_REG_SIZE;
/* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
* so it's aligned access and [off, off + size) are within stack limits
*/
if (value_regno >= 0 &&
is_spillable_regtype(state->regs[value_regno].type)) {
/* register containing pointer is being spilled into stack */
if (size != BPF_REG_SIZE) {
verbose("invalid size of register spill\n");
return -EACCES;
}
/* save register state */
state->spilled_regs[spi] = state->regs[value_regno];
state->spilled_regs[spi].live |= REG_LIVE_WRITTEN;
for (i = 0; i < BPF_REG_SIZE; i++)
state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
} else {
/* regular write of data into stack */
state->spilled_regs[spi] = (struct bpf_reg_state) {};
for (i = 0; i < size; i++)
state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
}
return 0;
}
static void mark_stack_slot_read(const struct bpf_verifier_state *state, int slot)
{
struct bpf_verifier_state *parent = state->parent;
while (parent) {
/* if read wasn't screened by an earlier write ... */
if (state->spilled_regs[slot].live & REG_LIVE_WRITTEN)
break;
/* ... then we depend on parent's value */
parent->spilled_regs[slot].live |= REG_LIVE_READ;
state = parent;
parent = state->parent;
}
}
static int check_stack_read(struct bpf_verifier_state *state, int off, int size,
int value_regno)
{
u8 *slot_type;
int i, spi;
slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
if (slot_type[0] == STACK_SPILL) {
if (size != BPF_REG_SIZE) {
verbose("invalid size of register spill\n");
return -EACCES;
}
for (i = 1; i < BPF_REG_SIZE; i++) {
if (slot_type[i] != STACK_SPILL) {
verbose("corrupted spill memory\n");
return -EACCES;
}
}
spi = (MAX_BPF_STACK + off) / BPF_REG_SIZE;
if (value_regno >= 0) {
/* restore register state from stack */
state->regs[value_regno] = state->spilled_regs[spi];
mark_stack_slot_read(state, spi);
}
return 0;
} else {
for (i = 0; i < size; i++) {
if (slot_type[i] != STACK_MISC) {
verbose("invalid read from stack off %d+%d size %d\n",
off, i, size);
return -EACCES;
}
}
if (value_regno >= 0)
/* have read misc data from the stack */
mark_reg_unknown(state->regs, value_regno);
return 0;
}
}
/* check read/write into map element returned by bpf_map_lookup_elem() */
static int __check_map_access(struct bpf_verifier_env *env, u32 regno, int off,
int size)
{
struct bpf_map *map = env->cur_state.regs[regno].map_ptr;
if (off < 0 || size <= 0 || off + size > map->value_size) {
verbose("invalid access to map value, value_size=%d off=%d size=%d\n",
map->value_size, off, size);
return -EACCES;
}
return 0;
}
/* check read/write into a map element with possible variable offset */
static int check_map_access(struct bpf_verifier_env *env, u32 regno,
int off, int size)
{
struct bpf_verifier_state *state = &env->cur_state;
struct bpf_reg_state *reg = &state->regs[regno];
int err;
/* We may have adjusted the register to this map value, so we
* need to try adding each of min_value and max_value to off
* to make sure our theoretical access will be safe.
*/
if (log_level)
print_verifier_state(state);
/* The minimum value is only important with signed
* comparisons where we can't assume the floor of a
* value is 0. If we are using signed variables for our
* index'es we need to make sure that whatever we use
* will have a set floor within our range.
*/
if (reg->smin_value < 0) {
verbose("R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
regno);
return -EACCES;
}
err = __check_map_access(env, regno, reg->smin_value + off, size);
if (err) {
verbose("R%d min value is outside of the array range\n", regno);
return err;
}
/* If we haven't set a max value then we need to bail since we can't be
* sure we won't do bad things.
* If reg->umax_value + off could overflow, treat that as unbounded too.
*/
if (reg->umax_value >= BPF_MAX_VAR_OFF) {
verbose("R%d unbounded memory access, make sure to bounds check any array access into a map\n",
regno);
return -EACCES;
}
err = __check_map_access(env, regno, reg->umax_value + off, size);
if (err)
verbose("R%d max value is outside of the array range\n", regno);
return err;
}
#define MAX_PACKET_OFF 0xffff
static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
const struct bpf_call_arg_meta *meta,
enum bpf_access_type t)
{
switch (env->prog->type) {
case BPF_PROG_TYPE_LWT_IN:
case BPF_PROG_TYPE_LWT_OUT:
/* dst_input() and dst_output() can't write for now */
if (t == BPF_WRITE)
return false;
/* fallthrough */
case BPF_PROG_TYPE_SCHED_CLS:
case BPF_PROG_TYPE_SCHED_ACT:
case BPF_PROG_TYPE_XDP:
case BPF_PROG_TYPE_LWT_XMIT:
case BPF_PROG_TYPE_SK_SKB:
if (meta)
return meta->pkt_access;
env->seen_direct_write = true;
return true;
default:
return false;
}
}
static int __check_packet_access(struct bpf_verifier_env *env, u32 regno,
int off, int size)
{
struct bpf_reg_state *regs = env->cur_state.regs;
struct bpf_reg_state *reg = &regs[regno];
if (off < 0 || size <= 0 || (u64)off + size > reg->range) {
verbose("invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
off, size, regno, reg->id, reg->off, reg->range);
return -EACCES;
}
return 0;
}
static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
int size)
{
struct bpf_reg_state *regs = env->cur_state.regs;
struct bpf_reg_state *reg = &regs[regno];
int err;
/* We may have added a variable offset to the packet pointer; but any
* reg->range we have comes after that. We are only checking the fixed
* offset.
*/
/* We don't allow negative numbers, because we aren't tracking enough
* detail to prove they're safe.
*/
if (reg->smin_value < 0) {
verbose("R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
regno);
return -EACCES;
}
err = __check_packet_access(env, regno, off, size);
if (err) {
verbose("R%d offset is outside of the packet\n", regno);
return err;
}
return err;
}
/* check access to 'struct bpf_context' fields. Supports fixed offsets only */
static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size,
enum bpf_access_type t, enum bpf_reg_type *reg_type)
{
struct bpf_insn_access_aux info = {
.reg_type = *reg_type,
};
/* for analyzer ctx accesses are already validated and converted */
if (env->analyzer_ops)
return 0;
if (env->prog->aux->ops->is_valid_access &&
env->prog->aux->ops->is_valid_access(off, size, t, &info)) {
/* A non zero info.ctx_field_size indicates that this field is a
* candidate for later verifier transformation to load the whole
* field and then apply a mask when accessed with a narrower
* access than actual ctx access size. A zero info.ctx_field_size
* will only allow for whole field access and rejects any other
* type of narrower access.
*/
env->insn_aux_data[insn_idx].ctx_field_size = info.ctx_field_size;
*reg_type = info.reg_type;
/* remember the offset of last byte accessed in ctx */
if (env->prog->aux->max_ctx_offset < off + size)
env->prog->aux->max_ctx_offset = off + size;
return 0;
}
verbose("invalid bpf_context access off=%d size=%d\n", off, size);
return -EACCES;
}
static bool __is_pointer_value(bool allow_ptr_leaks,
const struct bpf_reg_state *reg)
{
if (allow_ptr_leaks)
return false;
return reg->type != SCALAR_VALUE;
}
static bool is_pointer_value(struct bpf_verifier_env *env, int regno)
{
return __is_pointer_value(env->allow_ptr_leaks, &env->cur_state.regs[regno]);
}
static bool is_ctx_reg(struct bpf_verifier_env *env, int regno)
{
const struct bpf_reg_state *reg = &env->cur_state.regs[regno];
return reg->type == PTR_TO_CTX;
}
static bool is_pkt_reg(struct bpf_verifier_env *env, int regno)
{
const struct bpf_reg_state *reg = &env->cur_state.regs[regno];
return reg->type == PTR_TO_PACKET;
}
static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg,
int off, int size, bool strict)
{
struct tnum reg_off;
int ip_align;
/* Byte size accesses are always allowed. */
if (!strict || size == 1)
return 0;
/* For platforms that do not have a Kconfig enabling
* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS the value of
* NET_IP_ALIGN is universally set to '2'. And on platforms
* that do set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, we get
* to this code only in strict mode where we want to emulate
* the NET_IP_ALIGN==2 checking. Therefore use an
* unconditional IP align value of '2'.
*/
ip_align = 2;
reg_off = tnum_add(reg->var_off, tnum_const(ip_align + reg->off + off));
if (!tnum_is_aligned(reg_off, size)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose("misaligned packet access off %d+%s+%d+%d size %d\n",
ip_align, tn_buf, reg->off, off, size);
return -EACCES;
}
return 0;
}
static int check_generic_ptr_alignment(const struct bpf_reg_state *reg,
const char *pointer_desc,
int off, int size, bool strict)
{
struct tnum reg_off;
/* Byte size accesses are always allowed. */
if (!strict || size == 1)
return 0;
reg_off = tnum_add(reg->var_off, tnum_const(reg->off + off));
if (!tnum_is_aligned(reg_off, size)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose("misaligned %saccess off %s+%d+%d size %d\n",
pointer_desc, tn_buf, reg->off, off, size);
return -EACCES;
}
return 0;
}
static int check_ptr_alignment(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int off,
int size, bool strict_alignment_once)
{
bool strict = env->strict_alignment || strict_alignment_once;
const char *pointer_desc = "";
switch (reg->type) {
case PTR_TO_PACKET:
/* special case, because of NET_IP_ALIGN */
return check_pkt_ptr_alignment(reg, off, size, strict);
case PTR_TO_MAP_VALUE:
pointer_desc = "value ";
break;
case PTR_TO_CTX:
pointer_desc = "context ";
break;
case PTR_TO_STACK:
pointer_desc = "stack ";
/* The stack spill tracking logic in check_stack_write()
* and check_stack_read() relies on stack accesses being
* aligned.
*/
strict = true;
break;
default:
break;
}
return check_generic_ptr_alignment(reg, pointer_desc, off, size, strict);
}
/* truncate register to smaller size (in bytes)
* must be called with size < BPF_REG_SIZE
*/
static void coerce_reg_to_size(struct bpf_reg_state *reg, int size)
{
u64 mask;
/* clear high bits in bit representation */
reg->var_off = tnum_cast(reg->var_off, size);
/* fix arithmetic bounds */
mask = ((u64)1 << (size * 8)) - 1;
if ((reg->umin_value & ~mask) == (reg->umax_value & ~mask)) {
reg->umin_value &= mask;
reg->umax_value &= mask;
} else {
reg->umin_value = 0;
reg->umax_value = mask;
}
reg->smin_value = reg->umin_value;
reg->smax_value = reg->umax_value;
}
/* check whether memory at (regno + off) is accessible for t = (read | write)
* if t==write, value_regno is a register which value is stored into memory
* if t==read, value_regno is a register which will receive the value from memory
* if t==write && value_regno==-1, some unknown value is stored into memory
* if t==read && value_regno==-1, don't care what we read from memory
*/
static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regno,
int off, int bpf_size, enum bpf_access_type t,
int value_regno, bool strict_alignment_once)
{
struct bpf_verifier_state *state = &env->cur_state;
struct bpf_reg_state *reg = &state->regs[regno];
int size, err = 0;
size = bpf_size_to_bytes(bpf_size);
if (size < 0)
return size;
/* alignment checks will add in reg->off themselves */
err = check_ptr_alignment(env, reg, off, size, strict_alignment_once);
if (err)
return err;
/* for access checks, reg->off is just part of off */
off += reg->off;
if (reg->type == PTR_TO_MAP_VALUE) {
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose("R%d leaks addr into map\n", value_regno);
return -EACCES;
}
err = check_map_access(env, regno, off, size);
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown(state->regs, value_regno);
} else if (reg->type == PTR_TO_CTX) {
enum bpf_reg_type reg_type = SCALAR_VALUE;
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose("R%d leaks addr into ctx\n", value_regno);
return -EACCES;
}
/* ctx accesses must be at a fixed offset, so that we can
* determine what type of data were returned.
*/
if (reg->off) {
verbose("dereference of modified ctx ptr R%d off=%d+%d, ctx+const is allowed, ctx+const+const is not\n",
regno, reg->off, off - reg->off);
return -EACCES;
}
if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose("variable ctx access var_off=%s off=%d size=%d",
tn_buf, off, size);
return -EACCES;
}
err = check_ctx_access(env, insn_idx, off, size, t, &reg_type);
if (!err && t == BPF_READ && value_regno >= 0) {
/* ctx access returns either a scalar, or a
* PTR_TO_PACKET[_END]. In the latter case, we know
* the offset is zero.
*/
if (reg_type == SCALAR_VALUE)
mark_reg_unknown(state->regs, value_regno);
else
mark_reg_known_zero(state->regs, value_regno);
state->regs[value_regno].id = 0;
state->regs[value_regno].off = 0;
state->regs[value_regno].range = 0;
state->regs[value_regno].type = reg_type;
}
} else if (reg->type == PTR_TO_STACK) {
/* stack accesses must be at a fixed offset, so that we can
* determine what type of data were returned.
* See check_stack_read().
*/
if (!tnum_is_const(reg->var_off)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose("variable stack access var_off=%s off=%d size=%d",
tn_buf, off, size);
return -EACCES;
}
off += reg->var_off.value;
if (off >= 0 || off < -MAX_BPF_STACK) {
verbose("invalid stack off=%d size=%d\n", off, size);
return -EACCES;
}
if (env->prog->aux->stack_depth < -off)
env->prog->aux->stack_depth = -off;
if (t == BPF_WRITE) {
if (!env->allow_ptr_leaks &&
state->stack_slot_type[MAX_BPF_STACK + off] == STACK_SPILL &&
size != BPF_REG_SIZE) {
verbose("attempt to corrupt spilled pointer on stack\n");
return -EACCES;
}
err = check_stack_write(state, off, size, value_regno);
} else {
err = check_stack_read(state, off, size, value_regno);
}
} else if (reg->type == PTR_TO_PACKET) {
if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) {
verbose("cannot write into packet\n");
return -EACCES;
}
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose("R%d leaks addr into packet\n", value_regno);
return -EACCES;
}
err = check_packet_access(env, regno, off, size);
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown(state->regs, value_regno);
} else {
verbose("R%d invalid mem access '%s'\n",
regno, reg_type_str[reg->type]);
return -EACCES;
}
if (!err && size < BPF_REG_SIZE && value_regno >= 0 && t == BPF_READ &&
state->regs[value_regno].type == SCALAR_VALUE) {
/* b/h/w load zero-extends, mark upper bits as known 0 */
coerce_reg_to_size(&state->regs[value_regno], size);
}
return err;
}
static int check_xadd(struct bpf_verifier_env *env, int insn_idx, struct bpf_insn *insn)
{
int err;
if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
insn->imm != 0) {
verbose("BPF_XADD uses reserved fields\n");
return -EINVAL;
}
/* check src1 operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
/* check src2 operand */
err = check_reg_arg(env, insn->dst_reg, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, insn->src_reg)) {
verbose("R%d leaks addr into mem\n", insn->src_reg);
return -EACCES;
}
if (is_ctx_reg(env, insn->dst_reg) ||
is_pkt_reg(env, insn->dst_reg)) {
verbose("BPF_XADD stores into R%d %s is not allowed\n",
insn->dst_reg, is_ctx_reg(env, insn->dst_reg) ?
"context" : "packet");
return -EACCES;
}
/* check whether atomic_add can read the memory */
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_READ, -1, true);
if (err)
return err;
/* check whether atomic_add can write into the same memory */
return check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_WRITE, -1, true);
}
/* Does this register contain a constant zero? */
static bool register_is_null(struct bpf_reg_state reg)
{
return reg.type == SCALAR_VALUE && tnum_equals_const(reg.var_off, 0);
}
/* when register 'regno' is passed into function that will read 'access_size'
* bytes from that pointer, make sure that it's within stack boundary
* and all elements of stack are initialized.
* Unlike most pointer bounds-checking functions, this one doesn't take an
* 'off' argument, so it has to add in reg->off itself.
*/
static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
int access_size, bool zero_size_allowed,
struct bpf_call_arg_meta *meta)
{
struct bpf_verifier_state *state = &env->cur_state;
struct bpf_reg_state *regs = state->regs;
int off, i;
if (regs[regno].type != PTR_TO_STACK) {
/* Allow zero-byte read from NULL, regardless of pointer type */
if (zero_size_allowed && access_size == 0 &&
register_is_null(regs[regno]))
return 0;
verbose("R%d type=%s expected=%s\n", regno,
reg_type_str[regs[regno].type],
reg_type_str[PTR_TO_STACK]);
return -EACCES;
}
/* Only allow fixed-offset stack reads */
if (!tnum_is_const(regs[regno].var_off)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), regs[regno].var_off);
verbose("invalid variable stack read R%d var_off=%s\n",
regno, tn_buf);
return -EACCES;
}
off = regs[regno].off + regs[regno].var_off.value;
if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
access_size <= 0) {
verbose("invalid stack type R%d off=%d access_size=%d\n",
regno, off, access_size);
return -EACCES;
}
if (env->prog->aux->stack_depth < -off)
env->prog->aux->stack_depth = -off;
if (meta && meta->raw_mode) {
meta->access_size = access_size;
meta->regno = regno;
return 0;
}
for (i = 0; i < access_size; i++) {
if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
verbose("invalid indirect read from stack off %d+%d size %d\n",
off, i, access_size);
return -EACCES;
}
}
return 0;
}
static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
int access_size, bool zero_size_allowed,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *regs = env->cur_state.regs, *reg = &regs[regno];
switch (reg->type) {
case PTR_TO_PACKET:
return check_packet_access(env, regno, reg->off, access_size);
case PTR_TO_MAP_VALUE:
return check_map_access(env, regno, reg->off, access_size);
default: /* scalar_value|ptr_to_stack or invalid ptr */
return check_stack_boundary(env, regno, access_size,
zero_size_allowed, meta);
}
}
static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
enum bpf_arg_type arg_type,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *regs = env->cur_state.regs, *reg = &regs[regno];
enum bpf_reg_type expected_type, type = reg->type;
int err = 0;
if (arg_type == ARG_DONTCARE)
return 0;
err = check_reg_arg(env, regno, SRC_OP);
if (err)
return err;
if (arg_type == ARG_ANYTHING) {
if (is_pointer_value(env, regno)) {
verbose("R%d leaks addr into helper function\n", regno);
return -EACCES;
}
return 0;
}
if (type == PTR_TO_PACKET &&
!may_access_direct_pkt_data(env, meta, BPF_READ)) {
verbose("helper access to the packet is not allowed\n");
return -EACCES;
}
if (arg_type == ARG_PTR_TO_MAP_KEY ||
arg_type == ARG_PTR_TO_MAP_VALUE) {
expected_type = PTR_TO_STACK;
if (type != PTR_TO_PACKET && type != expected_type)
goto err_type;
} else if (arg_type == ARG_CONST_SIZE ||
arg_type == ARG_CONST_SIZE_OR_ZERO) {
expected_type = SCALAR_VALUE;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_CONST_MAP_PTR) {
expected_type = CONST_PTR_TO_MAP;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_PTR_TO_CTX) {
expected_type = PTR_TO_CTX;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_PTR_TO_MEM ||
arg_type == ARG_PTR_TO_UNINIT_MEM) {
expected_type = PTR_TO_STACK;
/* One exception here. In case function allows for NULL to be
* passed in as argument, it's a SCALAR_VALUE type. Final test
* happens during stack boundary checking.
*/
if (register_is_null(*reg))
/* final test in check_stack_boundary() */;
else if (type != PTR_TO_PACKET && type != PTR_TO_MAP_VALUE &&
type != expected_type)
goto err_type;
meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM;
} else {
verbose("unsupported arg_type %d\n", arg_type);
return -EFAULT;
}
if (arg_type == ARG_CONST_MAP_PTR) {
/* bpf_map_xxx(map_ptr) call: remember that map_ptr */
meta->map_ptr = reg->map_ptr;
} else if (arg_type == ARG_PTR_TO_MAP_KEY) {
/* bpf_map_xxx(..., map_ptr, ..., key) call:
* check that [key, key + map->key_size) are within
* stack limits and initialized
*/
if (!meta->map_ptr) {
/* in function declaration map_ptr must come before
* map_key, so that it's verified and known before
* we have to check map_key here. Otherwise it means
* that kernel subsystem misconfigured verifier
*/
verbose("invalid map_ptr to access map->key\n");
return -EACCES;
}
if (type == PTR_TO_PACKET)
err = check_packet_access(env, regno, reg->off,
meta->map_ptr->key_size);
else
err = check_stack_boundary(env, regno,
meta->map_ptr->key_size,
false, NULL);
} else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
/* bpf_map_xxx(..., map_ptr, ..., value) call:
* check [value, value + map->value_size) validity
*/
if (!meta->map_ptr) {
/* kernel subsystem misconfigured verifier */
verbose("invalid map_ptr to access map->value\n");
return -EACCES;
}
if (type == PTR_TO_PACKET)
err = check_packet_access(env, regno, reg->off,
meta->map_ptr->value_size);
else
err = check_stack_boundary(env, regno,
meta->map_ptr->value_size,
false, NULL);
} else if (arg_type == ARG_CONST_SIZE ||
arg_type == ARG_CONST_SIZE_OR_ZERO) {
bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);
/* bpf_xxx(..., buf, len) call will access 'len' bytes
* from stack pointer 'buf'. Check it
* note: regno == len, regno - 1 == buf
*/
if (regno == 0) {
/* kernel subsystem misconfigured verifier */
verbose("ARG_CONST_SIZE cannot be first argument\n");
return -EACCES;
}
/* The register is SCALAR_VALUE; the access check
* happens using its boundaries.
*/
if (!tnum_is_const(reg->var_off))
/* For unprivileged variable accesses, disable raw
* mode so that the program is required to
* initialize all the memory that the helper could
* just partially fill up.
*/
meta = NULL;
if (reg->smin_value < 0) {
verbose("R%d min value is negative, either use unsigned or 'var &= const'\n",
regno);
return -EACCES;
}
if (reg->umin_value == 0) {
err = check_helper_mem_access(env, regno - 1, 0,
zero_size_allowed,
meta);
if (err)
return err;
}
if (reg->umax_value >= BPF_MAX_VAR_SIZ) {
verbose("R%d unbounded memory access, use 'var &= const' or 'if (var < const)'\n",
regno);
return -EACCES;
}
err = check_helper_mem_access(env, regno - 1,
reg->umax_value,
zero_size_allowed, meta);
}
return err;
err_type:
verbose("R%d type=%s expected=%s\n", regno,
reg_type_str[type], reg_type_str[expected_type]);
return -EACCES;
}
static int check_map_func_compatibility(struct bpf_map *map, int func_id)
{
if (!map)
return 0;
/* We need a two way check, first is from map perspective ... */
switch (map->map_type) {
case BPF_MAP_TYPE_PROG_ARRAY:
if (func_id != BPF_FUNC_tail_call)
goto error;
break;
case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
if (func_id != BPF_FUNC_perf_event_read &&
func_id != BPF_FUNC_perf_event_output)
goto error;
break;
case BPF_MAP_TYPE_STACK_TRACE:
if (func_id != BPF_FUNC_get_stackid)
goto error;
break;
case BPF_MAP_TYPE_CGROUP_ARRAY:
if (func_id != BPF_FUNC_skb_under_cgroup &&
func_id != BPF_FUNC_current_task_under_cgroup)
goto error;
break;
/* devmap returns a pointer to a live net_device ifindex that we cannot
* allow to be modified from bpf side. So do not allow lookup elements
* for now.
*/
case BPF_MAP_TYPE_DEVMAP:
if (func_id != BPF_FUNC_redirect_map)
goto error;
break;
case BPF_MAP_TYPE_ARRAY_OF_MAPS:
case BPF_MAP_TYPE_HASH_OF_MAPS:
if (func_id != BPF_FUNC_map_lookup_elem)
goto error;
break;
case BPF_MAP_TYPE_SOCKMAP:
if (func_id != BPF_FUNC_sk_redirect_map &&
func_id != BPF_FUNC_sock_map_update &&
func_id != BPF_FUNC_map_delete_elem)
goto error;
break;
default:
break;
}
/* ... and second from the function itself. */
switch (func_id) {
case BPF_FUNC_tail_call:
if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
goto error;
break;
case BPF_FUNC_perf_event_read:
case BPF_FUNC_perf_event_output:
if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
goto error;
break;
case BPF_FUNC_get_stackid:
if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
goto error;
break;
case BPF_FUNC_current_task_under_cgroup:
case BPF_FUNC_skb_under_cgroup:
if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)
goto error;
break;
case BPF_FUNC_redirect_map:
if (map->map_type != BPF_MAP_TYPE_DEVMAP)
goto error;
break;
case BPF_FUNC_sk_redirect_map:
if (map->map_type != BPF_MAP_TYPE_SOCKMAP)
goto error;
break;
case BPF_FUNC_sock_map_update:
if (map->map_type != BPF_MAP_TYPE_SOCKMAP)
goto error;
break;
default:
break;
}
return 0;
error:
verbose("cannot pass map_type %d into func %s#%d\n",
map->map_type, func_id_name(func_id), func_id);
return -EINVAL;
}
static int check_raw_mode(const struct bpf_func_proto *fn)
{
int count = 0;
if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM)
count++;
return count > 1 ? -EINVAL : 0;
}
/* Packet data might have moved, any old PTR_TO_PACKET[_END] are now invalid,
* so turn them into unknown SCALAR_VALUE.
*/
static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
{
struct bpf_verifier_state *state = &env->cur_state;
struct bpf_reg_state *regs = state->regs, *reg;
int i;
for (i = 0; i < MAX_BPF_REG; i++)
if (regs[i].type == PTR_TO_PACKET ||
regs[i].type == PTR_TO_PACKET_END)
mark_reg_unknown(regs, i);
for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
if (state->stack_slot_type[i] != STACK_SPILL)
continue;
reg = &state->spilled_regs[i / BPF_REG_SIZE];
if (reg->type != PTR_TO_PACKET &&
reg->type != PTR_TO_PACKET_END)
continue;
__mark_reg_unknown(reg);
}
}
static int check_call(struct bpf_verifier_env *env, int func_id, int insn_idx)
{
struct bpf_verifier_state *state = &env->cur_state;
const struct bpf_func_proto *fn = NULL;
struct bpf_reg_state *regs = state->regs;
struct bpf_call_arg_meta meta;
bool changes_data;
int i, err;
/* find function prototype */
if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
verbose("invalid func %s#%d\n", func_id_name(func_id), func_id);
return -EINVAL;
}
if (env->prog->aux->ops->get_func_proto)
fn = env->prog->aux->ops->get_func_proto(func_id);
if (!fn) {
verbose("unknown func %s#%d\n", func_id_name(func_id), func_id);
return -EINVAL;
}
/* eBPF programs must be GPL compatible to use GPL-ed functions */
if (!env->prog->gpl_compatible && fn->gpl_only) {
verbose("cannot call GPL only function from proprietary program\n");
return -EINVAL;
}
changes_data = bpf_helper_changes_pkt_data(fn->func);
memset(&meta, 0, sizeof(meta));
meta.pkt_access = fn->pkt_access;
/* We only support one arg being in raw mode at the moment, which
* is sufficient for the helper functions we have right now.
*/
err = check_raw_mode(fn);
if (err) {
verbose("kernel subsystem misconfigured func %s#%d\n",
func_id_name(func_id), func_id);
return err;
}
/* check args */
err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
if (err)
return err;
if (func_id == BPF_FUNC_tail_call) {
if (meta.map_ptr == NULL) {
verbose("verifier bug\n");
return -EINVAL;
}
env->insn_aux_data[insn_idx].map_ptr = meta.map_ptr;
}
err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta);
if (err)
return err;
/* Mark slots with STACK_MISC in case of raw mode, stack offset
* is inferred from register state.
*/
for (i = 0; i < meta.access_size; i++) {
err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B,
BPF_WRITE, -1, false);
if (err)
return err;
}
/* reset caller saved regs */
for (i = 0; i < CALLER_SAVED_REGS; i++) {
mark_reg_not_init(regs, caller_saved[i]);
check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
}
/* update return register (already marked as written above) */
if (fn->ret_type == RET_INTEGER) {
/* sets type to SCALAR_VALUE */
mark_reg_unknown(regs, BPF_REG_0);
} else if (fn->ret_type == RET_VOID) {
regs[BPF_REG_0].type = NOT_INIT;
} else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
struct bpf_insn_aux_data *insn_aux;
regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
/* There is no offset yet applied, variable or fixed */
mark_reg_known_zero(regs, BPF_REG_0);
regs[BPF_REG_0].off = 0;
/* remember map_ptr, so that check_map_access()
* can check 'value_size' boundary of memory access
* to map element returned from bpf_map_lookup_elem()
*/
if (meta.map_ptr == NULL) {
verbose("kernel subsystem misconfigured verifier\n");
return -EINVAL;
}
regs[BPF_REG_0].map_ptr = meta.map_ptr;
regs[BPF_REG_0].id = ++env->id_gen;
insn_aux = &env->insn_aux_data[insn_idx];
if (!insn_aux->map_ptr)
insn_aux->map_ptr = meta.map_ptr;
else if (insn_aux->map_ptr != meta.map_ptr)
insn_aux->map_ptr = BPF_MAP_PTR_POISON;
} else {
verbose("unknown return type %d of func %s#%d\n",
fn->ret_type, func_id_name(func_id), func_id);
return -EINVAL;
}
err = check_map_func_compatibility(meta.map_ptr, func_id);
if (err)
return err;
if (changes_data)
clear_all_pkt_pointers(env);
return 0;
}
static bool signed_add_overflows(s64 a, s64 b)
{
/* Do the add in u64, where overflow is well-defined */
s64 res = (s64)((u64)a + (u64)b);
if (b < 0)
return res > a;
return res < a;
}
static bool signed_sub_overflows(s64 a, s64 b)
{
/* Do the sub in u64, where overflow is well-defined */
s64 res = (s64)((u64)a - (u64)b);
if (b < 0)
return res < a;
return res > a;
}
static bool check_reg_sane_offset(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg,
enum bpf_reg_type type)
{
bool known = tnum_is_const(reg->var_off);
s64 val = reg->var_off.value;
s64 smin = reg->smin_value;
if (known && (val >= BPF_MAX_VAR_OFF || val <= -BPF_MAX_VAR_OFF)) {
verbose("math between %s pointer and %lld is not allowed\n",
reg_type_str[type], val);
return false;
}
if (reg->off >= BPF_MAX_VAR_OFF || reg->off <= -BPF_MAX_VAR_OFF) {
verbose("%s pointer offset %d is not allowed\n",
reg_type_str[type], reg->off);
return false;
}
if (smin == S64_MIN) {
verbose("math between %s pointer and register with unbounded min value is not allowed\n",
reg_type_str[type]);
return false;
}
if (smin >= BPF_MAX_VAR_OFF || smin <= -BPF_MAX_VAR_OFF) {
verbose("value %lld makes %s pointer be out of bounds\n",
smin, reg_type_str[type]);
return false;
}
return true;
}
/* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off.
* Caller should also handle BPF_MOV case separately.
* If we return -EACCES, caller may want to try again treating pointer as a
* scalar. So we only emit a diagnostic if !env->allow_ptr_leaks.
*/
static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
struct bpf_insn *insn,
const struct bpf_reg_state *ptr_reg,
const struct bpf_reg_state *off_reg)
{
struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg;
bool known = tnum_is_const(off_reg->var_off);
s64 smin_val = off_reg->smin_value, smax_val = off_reg->smax_value,
smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value;
u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value,
umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value;
u8 opcode = BPF_OP(insn->code);
u32 dst = insn->dst_reg;
dst_reg = &regs[dst];
if ((known && (smin_val != smax_val || umin_val != umax_val)) ||
smin_val > smax_val || umin_val > umax_val) {
/* Taint dst register if offset had invalid bounds derived from
* e.g. dead branches.
*/
__mark_reg_unknown(dst_reg);
return 0;
}
if (BPF_CLASS(insn->code) != BPF_ALU64) {
/* 32-bit ALU ops on pointers produce (meaningless) scalars */
if (!env->allow_ptr_leaks)
verbose("R%d 32-bit pointer arithmetic prohibited\n",
dst);
return -EACCES;
}
if (ptr_reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
if (!env->allow_ptr_leaks)
verbose("R%d pointer arithmetic on PTR_TO_MAP_VALUE_OR_NULL prohibited, null-check it first\n",
dst);
return -EACCES;
}
if (ptr_reg->type == CONST_PTR_TO_MAP) {
if (!env->allow_ptr_leaks)
verbose("R%d pointer arithmetic on CONST_PTR_TO_MAP prohibited\n",
dst);
return -EACCES;
}
if (ptr_reg->type == PTR_TO_PACKET_END) {
if (!env->allow_ptr_leaks)
verbose("R%d pointer arithmetic on PTR_TO_PACKET_END prohibited\n",
dst);
return -EACCES;
}
/* In case of 'scalar += pointer', dst_reg inherits pointer type and id.
* The id may be overwritten later if we create a new variable offset.
*/
dst_reg->type = ptr_reg->type;
dst_reg->id = ptr_reg->id;
if (!check_reg_sane_offset(env, off_reg, ptr_reg->type) ||
!check_reg_sane_offset(env, ptr_reg, ptr_reg->type))
return -EINVAL;
switch (opcode) {
case BPF_ADD:
/* We can take a fixed offset as long as it doesn't overflow
* the s32 'off' field
*/
if (known && (ptr_reg->off + smin_val ==
(s64)(s32)(ptr_reg->off + smin_val))) {
/* pointer += K. Accumulate it into fixed offset */
dst_reg->smin_value = smin_ptr;
dst_reg->smax_value = smax_ptr;
dst_reg->umin_value = umin_ptr;
dst_reg->umax_value = umax_ptr;
dst_reg->var_off = ptr_reg->var_off;
dst_reg->off = ptr_reg->off + smin_val;
dst_reg->range = ptr_reg->range;
break;
}
/* A new variable offset is created. Note that off_reg->off
* == 0, since it's a scalar.
* dst_reg gets the pointer type and since some positive
* integer value was added to the pointer, give it a new 'id'
* if it's a PTR_TO_PACKET.
* this creates a new 'base' pointer, off_reg (variable) gets
* added into the variable offset, and we copy the fixed offset
* from ptr_reg.
*/
if (signed_add_overflows(smin_ptr, smin_val) ||
signed_add_overflows(smax_ptr, smax_val)) {
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
dst_reg->smin_value = smin_ptr + smin_val;
dst_reg->smax_value = smax_ptr + smax_val;
}
if (umin_ptr + umin_val < umin_ptr ||
umax_ptr + umax_val < umax_ptr) {
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
} else {
dst_reg->umin_value = umin_ptr + umin_val;
dst_reg->umax_value = umax_ptr + umax_val;
}
dst_reg->var_off = tnum_add(ptr_reg->var_off, off_reg->var_off);
dst_reg->off = ptr_reg->off;
if (ptr_reg->type == PTR_TO_PACKET) {
dst_reg->id = ++env->id_gen;
/* something was added to pkt_ptr, set range to zero */
dst_reg->range = 0;
}
break;
case BPF_SUB:
if (dst_reg == off_reg) {
/* scalar -= pointer. Creates an unknown scalar */
if (!env->allow_ptr_leaks)
verbose("R%d tried to subtract pointer from scalar\n",
dst);
return -EACCES;
}
/* We don't allow subtraction from FP, because (according to
* test_verifier.c test "invalid fp arithmetic", JITs might not
* be able to deal with it.
*/
if (ptr_reg->type == PTR_TO_STACK) {
if (!env->allow_ptr_leaks)
verbose("R%d subtraction from stack pointer prohibited\n",
dst);
return -EACCES;
}
if (known && (ptr_reg->off - smin_val ==
(s64)(s32)(ptr_reg->off - smin_val))) {
/* pointer -= K. Subtract it from fixed offset */
dst_reg->smin_value = smin_ptr;
dst_reg->smax_value = smax_ptr;
dst_reg->umin_value = umin_ptr;
dst_reg->umax_value = umax_ptr;
dst_reg->var_off = ptr_reg->var_off;
dst_reg->id = ptr_reg->id;
dst_reg->off = ptr_reg->off - smin_val;
dst_reg->range = ptr_reg->range;
break;
}
/* A new variable offset is created. If the subtrahend is known
* nonnegative, then any reg->range we had before is still good.
*/
if (signed_sub_overflows(smin_ptr, smax_val) ||
signed_sub_overflows(smax_ptr, smin_val)) {
/* Overflow possible, we know nothing */
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
dst_reg->smin_value = smin_ptr - smax_val;
dst_reg->smax_value = smax_ptr - smin_val;
}
if (umin_ptr < umax_val) {
/* Overflow possible, we know nothing */
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
} else {
/* Cannot overflow (as long as bounds are consistent) */
dst_reg->umin_value = umin_ptr - umax_val;
dst_reg->umax_value = umax_ptr - umin_val;
}
dst_reg->var_off = tnum_sub(ptr_reg->var_off, off_reg->var_off);
dst_reg->off = ptr_reg->off;
if (ptr_reg->type == PTR_TO_PACKET) {
dst_reg->id = ++env->id_gen;
/* something was added to pkt_ptr, set range to zero */
if (smin_val < 0)
dst_reg->range = 0;
}
break;
case BPF_AND:
case BPF_OR:
case BPF_XOR:
/* bitwise ops on pointers are troublesome, prohibit for now.
* (However, in principle we could allow some cases, e.g.
* ptr &= ~3 which would reduce min_value by 3.)
*/
if (!env->allow_ptr_leaks)
verbose("R%d bitwise operator %s on pointer prohibited\n",
dst, bpf_alu_string[opcode >> 4]);
return -EACCES;
default:
/* other operators (e.g. MUL,LSH) produce non-pointer results */
if (!env->allow_ptr_leaks)
verbose("R%d pointer arithmetic with %s operator prohibited\n",
dst, bpf_alu_string[opcode >> 4]);
return -EACCES;
}
if (!check_reg_sane_offset(env, dst_reg, ptr_reg->type))
return -EINVAL;
__update_reg_bounds(dst_reg);
__reg_deduce_bounds(dst_reg);
__reg_bound_offset(dst_reg);
return 0;
}
/* WARNING: This function does calculations on 64-bit values, but the actual
* execution may occur on 32-bit values. Therefore, things like bitshifts
* need extra checks in the 32-bit case.
*/
static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
struct bpf_insn *insn,
struct bpf_reg_state *dst_reg,
struct bpf_reg_state src_reg)
{
struct bpf_reg_state *regs = env->cur_state.regs;
u8 opcode = BPF_OP(insn->code);
bool src_known, dst_known;
s64 smin_val, smax_val;
u64 umin_val, umax_val;
u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;
smin_val = src_reg.smin_value;
smax_val = src_reg.smax_value;
umin_val = src_reg.umin_value;
umax_val = src_reg.umax_value;
src_known = tnum_is_const(src_reg.var_off);
dst_known = tnum_is_const(dst_reg->var_off);
if ((src_known && (smin_val != smax_val || umin_val != umax_val)) ||
smin_val > smax_val || umin_val > umax_val) {
/* Taint dst register if offset had invalid bounds derived from
* e.g. dead branches.
*/
__mark_reg_unknown(dst_reg);
return 0;
}
if (!src_known &&
opcode != BPF_ADD && opcode != BPF_SUB && opcode != BPF_AND) {
__mark_reg_unknown(dst_reg);
return 0;
}
switch (opcode) {
case BPF_ADD:
if (signed_add_overflows(dst_reg->smin_value, smin_val) ||
signed_add_overflows(dst_reg->smax_value, smax_val)) {
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
dst_reg->smin_value += smin_val;
dst_reg->smax_value += smax_val;
}
if (dst_reg->umin_value + umin_val < umin_val ||
dst_reg->umax_value + umax_val < umax_val) {
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
} else {
dst_reg->umin_value += umin_val;
dst_reg->umax_value += umax_val;
}
dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off);
break;
case BPF_SUB:
if (signed_sub_overflows(dst_reg->smin_value, smax_val) ||
signed_sub_overflows(dst_reg->smax_value, smin_val)) {
/* Overflow possible, we know nothing */
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
dst_reg->smin_value -= smax_val;
dst_reg->smax_value -= smin_val;
}
if (dst_reg->umin_value < umax_val) {
/* Overflow possible, we know nothing */
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
} else {
/* Cannot overflow (as long as bounds are consistent) */
dst_reg->umin_value -= umax_val;
dst_reg->umax_value -= umin_val;
}
dst_reg->var_off = tnum_sub(dst_reg->var_off, src_reg.var_off);
break;
case BPF_MUL:
dst_reg->var_off = tnum_mul(dst_reg->var_off, src_reg.var_off);
if (smin_val < 0 || dst_reg->smin_value < 0) {
/* Ain't nobody got time to multiply that sign */
__mark_reg_unbounded(dst_reg);
__update_reg_bounds(dst_reg);
break;
}
/* Both values are positive, so we can work with unsigned and
* copy the result to signed (unless it exceeds S64_MAX).
*/
if (umax_val > U32_MAX || dst_reg->umax_value > U32_MAX) {
/* Potential overflow, we know nothing */
__mark_reg_unbounded(dst_reg);
/* (except what we can learn from the var_off) */
__update_reg_bounds(dst_reg);
break;
}
dst_reg->umin_value *= umin_val;
dst_reg->umax_value *= umax_val;
if (dst_reg->umax_value > S64_MAX) {
/* Overflow possible, we know nothing */
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
dst_reg->smin_value = dst_reg->umin_value;
dst_reg->smax_value = dst_reg->umax_value;
}
break;
case BPF_AND:
if (src_known && dst_known) {
__mark_reg_known(dst_reg, dst_reg->var_off.value &
src_reg.var_off.value);
break;
}
/* We get our minimum from the var_off, since that's inherently
* bitwise. Our maximum is the minimum of the operands' maxima.
*/
dst_reg->var_off = tnum_and(dst_reg->var_off, src_reg.var_off);
dst_reg->umin_value = dst_reg->var_off.value;
dst_reg->umax_value = min(dst_reg->umax_value, umax_val);
if (dst_reg->smin_value < 0 || smin_val < 0) {
/* Lose signed bounds when ANDing negative numbers,
* ain't nobody got time for that.
*/
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
/* ANDing two positives gives a positive, so safe to
* cast result into s64.
*/
dst_reg->smin_value = dst_reg->umin_value;
dst_reg->smax_value = dst_reg->umax_value;
}
/* We may learn something more from the var_off */
__update_reg_bounds(dst_reg);
break;
case BPF_OR:
if (src_known && dst_known) {
__mark_reg_known(dst_reg, dst_reg->var_off.value |
src_reg.var_off.value);
break;
}
/* We get our maximum from the var_off, and our minimum is the
* maximum of the operands' minima
*/
dst_reg->var_off = tnum_or(dst_reg->var_off, src_reg.var_off);
dst_reg->umin_value = max(dst_reg->umin_value, umin_val);
dst_reg->umax_value = dst_reg->var_off.value |
dst_reg->var_off.mask;
if (dst_reg->smin_value < 0 || smin_val < 0) {
/* Lose signed bounds when ORing negative numbers,
* ain't nobody got time for that.
*/
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
/* ORing two positives gives a positive, so safe to
* cast result into s64.
*/
dst_reg->smin_value = dst_reg->umin_value;
dst_reg->smax_value = dst_reg->umax_value;
}
/* We may learn something more from the var_off */
__update_reg_bounds(dst_reg);
break;
case BPF_LSH:
if (umax_val >= insn_bitness) {
/* Shifts greater than 31 or 63 are undefined.
* This includes shifts by a negative number.
*/
mark_reg_unknown(regs, insn->dst_reg);
break;
}
/* We lose all sign bit information (except what we can pick
* up from var_off)
*/
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
/* If we might shift our top bit out, then we know nothing */
if (dst_reg->umax_value > 1ULL << (63 - umax_val)) {
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
} else {
dst_reg->umin_value <<= umin_val;
dst_reg->umax_value <<= umax_val;
}
if (src_known)
dst_reg->var_off = tnum_lshift(dst_reg->var_off, umin_val);
else
dst_reg->var_off = tnum_lshift(tnum_unknown, umin_val);
/* We may learn something more from the var_off */
__update_reg_bounds(dst_reg);
break;
case BPF_RSH:
if (umax_val >= insn_bitness) {
/* Shifts greater than 31 or 63 are undefined.
* This includes shifts by a negative number.
*/
mark_reg_unknown(regs, insn->dst_reg);
break;
}
/* BPF_RSH is an unsigned shift. If the value in dst_reg might
* be negative, then either:
* 1) src_reg might be zero, so the sign bit of the result is
* unknown, so we lose our signed bounds
* 2) it's known negative, thus the unsigned bounds capture the
* signed bounds
* 3) the signed bounds cross zero, so they tell us nothing
* about the result
* If the value in dst_reg is known nonnegative, then again the
* unsigned bounts capture the signed bounds.
* Thus, in all cases it suffices to blow away our signed bounds
* and rely on inferring new ones from the unsigned bounds and
* var_off of the result.
*/
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
if (src_known)
dst_reg->var_off = tnum_rshift(dst_reg->var_off,
umin_val);
else
dst_reg->var_off = tnum_rshift(tnum_unknown, umin_val);
dst_reg->umin_value >>= umax_val;
dst_reg->umax_value >>= umin_val;
/* We may learn something more from the var_off */
__update_reg_bounds(dst_reg);
break;
default:
mark_reg_unknown(regs, insn->dst_reg);
break;
}
if (BPF_CLASS(insn->code) != BPF_ALU64) {
/* 32-bit ALU ops are (32,32)->32 */
coerce_reg_to_size(dst_reg, 4);
coerce_reg_to_size(&src_reg, 4);
}
__reg_deduce_bounds(dst_reg);
__reg_bound_offset(dst_reg);
return 0;
}
/* Handles ALU ops other than BPF_END, BPF_NEG and BPF_MOV: computes new min/max
* and var_off.
*/
static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs, *dst_reg, *src_reg;
struct bpf_reg_state *ptr_reg = NULL, off_reg = {0};
u8 opcode = BPF_OP(insn->code);
int rc;
dst_reg = &regs[insn->dst_reg];
src_reg = NULL;
if (dst_reg->type != SCALAR_VALUE)
ptr_reg = dst_reg;
if (BPF_SRC(insn->code) == BPF_X) {
src_reg = &regs[insn->src_reg];
if (src_reg->type != SCALAR_VALUE) {
if (dst_reg->type != SCALAR_VALUE) {
/* Combining two pointers by any ALU op yields
* an arbitrary scalar.
*/
if (!env->allow_ptr_leaks) {
verbose("R%d pointer %s pointer prohibited\n",
insn->dst_reg,
bpf_alu_string[opcode >> 4]);
return -EACCES;
}
mark_reg_unknown(regs, insn->dst_reg);
return 0;
} else {
/* scalar += pointer
* This is legal, but we have to reverse our
* src/dest handling in computing the range
*/
rc = adjust_ptr_min_max_vals(env, insn,
src_reg, dst_reg);
if (rc == -EACCES && env->allow_ptr_leaks) {
/* scalar += unknown scalar */
__mark_reg_unknown(&off_reg);
return adjust_scalar_min_max_vals(
env, insn,
dst_reg, off_reg);
}
return rc;
}
} else if (ptr_reg) {
/* pointer += scalar */
rc = adjust_ptr_min_max_vals(env, insn,
dst_reg, src_reg);
if (rc == -EACCES && env->allow_ptr_leaks) {
/* unknown scalar += scalar */
__mark_reg_unknown(dst_reg);
return adjust_scalar_min_max_vals(
env, insn, dst_reg, *src_reg);
}
return rc;
}
} else {
/* Pretend the src is a reg with a known value, since we only
* need to be able to read from this state.
*/
off_reg.type = SCALAR_VALUE;
__mark_reg_known(&off_reg, insn->imm);
src_reg = &off_reg;
if (ptr_reg) { /* pointer += K */
rc = adjust_ptr_min_max_vals(env, insn,
ptr_reg, src_reg);
if (rc == -EACCES && env->allow_ptr_leaks) {
/* unknown scalar += K */
__mark_reg_unknown(dst_reg);
return adjust_scalar_min_max_vals(
env, insn, dst_reg, off_reg);
}
return rc;
}
}
/* Got here implies adding two SCALAR_VALUEs */
if (WARN_ON_ONCE(ptr_reg)) {
print_verifier_state(&env->cur_state);
verbose("verifier internal error: unexpected ptr_reg\n");
return -EINVAL;
}
if (WARN_ON(!src_reg)) {
print_verifier_state(&env->cur_state);
verbose("verifier internal error: no src_reg\n");
return -EINVAL;
}
return adjust_scalar_min_max_vals(env, insn, dst_reg, *src_reg);
}
/* check validity of 32-bit and 64-bit arithmetic operations */
static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs;
u8 opcode = BPF_OP(insn->code);
int err;
if (opcode == BPF_END || opcode == BPF_NEG) {
if (opcode == BPF_NEG) {
if (BPF_SRC(insn->code) != 0 ||
insn->src_reg != BPF_REG_0 ||
insn->off != 0 || insn->imm != 0) {
verbose("BPF_NEG uses reserved fields\n");
return -EINVAL;
}
} else {
if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
(insn->imm != 16 && insn->imm != 32 && insn->imm != 64) ||
BPF_CLASS(insn->code) == BPF_ALU64) {
verbose("BPF_END uses reserved fields\n");
return -EINVAL;
}
}
/* check src operand */
err = check_reg_arg(env, insn->dst_reg, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, insn->dst_reg)) {
verbose("R%d pointer arithmetic prohibited\n",
insn->dst_reg);
return -EACCES;
}
/* check dest operand */
err = check_reg_arg(env, insn->dst_reg, DST_OP);
if (err)
return err;
} else if (opcode == BPF_MOV) {
if (BPF_SRC(insn->code) == BPF_X) {
if (insn->imm != 0 || insn->off != 0) {
verbose("BPF_MOV uses reserved fields\n");
return -EINVAL;
}
/* check src operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
} else {
if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
verbose("BPF_MOV uses reserved fields\n");
return -EINVAL;
}
}
/* check dest operand */
err = check_reg_arg(env, insn->dst_reg, DST_OP);
if (err)
return err;
if (BPF_SRC(insn->code) == BPF_X) {
if (BPF_CLASS(insn->code) == BPF_ALU64) {
/* case: R1 = R2
* copy register state to dest reg
*/
regs[insn->dst_reg] = regs[insn->src_reg];
regs[insn->dst_reg].live |= REG_LIVE_WRITTEN;
} else {
/* R1 = (u32) R2 */
if (is_pointer_value(env, insn->src_reg)) {
verbose("R%d partial copy of pointer\n",
insn->src_reg);
return -EACCES;
}
mark_reg_unknown(regs, insn->dst_reg);
coerce_reg_to_size(&regs[insn->dst_reg], 4);
}
} else {
/* case: R = imm
* remember the value we stored into this reg
*/
regs[insn->dst_reg].type = SCALAR_VALUE;
if (BPF_CLASS(insn->code) == BPF_ALU64) {
__mark_reg_known(regs + insn->dst_reg,
insn->imm);
} else {
__mark_reg_known(regs + insn->dst_reg,
(u32)insn->imm);
}
}
} else if (opcode > BPF_END) {
verbose("invalid BPF_ALU opcode %x\n", opcode);
return -EINVAL;
} else { /* all other ALU ops: and, sub, xor, add, ... */
if (BPF_SRC(insn->code) == BPF_X) {
if (insn->imm != 0 || insn->off != 0) {
verbose("BPF_ALU uses reserved fields\n");
return -EINVAL;
}
/* check src1 operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
} else {
if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
verbose("BPF_ALU uses reserved fields\n");
return -EINVAL;
}
}
/* check src2 operand */
err = check_reg_arg(env, insn->dst_reg, SRC_OP);
if (err)
return err;
if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
verbose("div by zero\n");
return -EINVAL;
}
if (opcode == BPF_ARSH && BPF_CLASS(insn->code) != BPF_ALU64) {
verbose("BPF_ARSH not supported for 32 bit ALU\n");
return -EINVAL;
}
if ((opcode == BPF_LSH || opcode == BPF_RSH ||
opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
if (insn->imm < 0 || insn->imm >= size) {
verbose("invalid shift %d\n", insn->imm);
return -EINVAL;
}
}
/* check dest operand */
err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
if (err)
return err;
return adjust_reg_min_max_vals(env, insn);
}
return 0;
}
static void find_good_pkt_pointers(struct bpf_verifier_state *state,
struct bpf_reg_state *dst_reg,
bool range_right_open)
{
struct bpf_reg_state *regs = state->regs, *reg;
u16 new_range;
int i;
if (dst_reg->off < 0 ||
(dst_reg->off == 0 && range_right_open))
/* This doesn't give us any range */
return;
if (dst_reg->umax_value > MAX_PACKET_OFF ||
dst_reg->umax_value + dst_reg->off > MAX_PACKET_OFF)
/* Risk of overflow. For instance, ptr + (1<<63) may be less
* than pkt_end, but that's because it's also less than pkt.
*/
return;
new_range = dst_reg->off;
if (range_right_open)
new_range--;
/* Examples for register markings:
*
* pkt_data in dst register:
*
* r2 = r3;
* r2 += 8;
* if (r2 > pkt_end) goto <handle exception>
* <access okay>
*
* r2 = r3;
* r2 += 8;
* if (r2 < pkt_end) goto <access okay>
* <handle exception>
*
* Where:
* r2 == dst_reg, pkt_end == src_reg
* r2=pkt(id=n,off=8,r=0)
* r3=pkt(id=n,off=0,r=0)
*
* pkt_data in src register:
*
* r2 = r3;
* r2 += 8;
* if (pkt_end >= r2) goto <access okay>
* <handle exception>
*
* r2 = r3;
* r2 += 8;
* if (pkt_end <= r2) goto <handle exception>
* <access okay>
*
* Where:
* pkt_end == dst_reg, r2 == src_reg
* r2=pkt(id=n,off=8,r=0)
* r3=pkt(id=n,off=0,r=0)
*
* Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8)
* or r3=pkt(id=n,off=0,r=8-1), so that range of bytes [r3, r3 + 8)
* and [r3, r3 + 8-1) respectively is safe to access depending on
* the check.
*/
/* If our ids match, then we must have the same max_value. And we
* don't care about the other reg's fixed offset, since if it's too big
* the range won't allow anything.
* dst_reg->off is known < MAX_PACKET_OFF, therefore it fits in a u16.
*/
for (i = 0; i < MAX_BPF_REG; i++)
if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id)
/* keep the maximum range already checked */
regs[i].range = max(regs[i].range, new_range);
for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
if (state->stack_slot_type[i] != STACK_SPILL)
continue;
reg = &state->spilled_regs[i / BPF_REG_SIZE];
if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id)
reg->range = max(reg->range, new_range);
}
}
/* Adjusts the register min/max values in the case that the dst_reg is the
* variable register that we are working on, and src_reg is a constant or we're
* simply doing a BPF_K check.
* In JEQ/JNE cases we also adjust the var_off values.
*/
static void reg_set_min_max(struct bpf_reg_state *true_reg,
struct bpf_reg_state *false_reg, u64 val,
u8 opcode)
{
/* If the dst_reg is a pointer, we can't learn anything about its
* variable offset from the compare (unless src_reg were a pointer into
* the same object, but we don't bother with that.
* Since false_reg and true_reg have the same type by construction, we
* only need to check one of them for pointerness.
*/
if (__is_pointer_value(false, false_reg))
return;
switch (opcode) {
case BPF_JEQ:
/* If this is false then we know nothing Jon Snow, but if it is
* true then we know for sure.
*/
__mark_reg_known(true_reg, val);
break;
case BPF_JNE:
/* If this is true we know nothing Jon Snow, but if it is false
* we know the value for sure;
*/
__mark_reg_known(false_reg, val);
break;
case BPF_JGT:
false_reg->umax_value = min(false_reg->umax_value, val);
true_reg->umin_value = max(true_reg->umin_value, val + 1);
break;
case BPF_JSGT:
false_reg->smax_value = min_t(s64, false_reg->smax_value, val);
true_reg->smin_value = max_t(s64, true_reg->smin_value, val + 1);
break;
case BPF_JLT:
false_reg->umin_value = max(false_reg->umin_value, val);
true_reg->umax_value = min(true_reg->umax_value, val - 1);
break;
case BPF_JSLT:
false_reg->smin_value = max_t(s64, false_reg->smin_value, val);
true_reg->smax_value = min_t(s64, true_reg->smax_value, val - 1);
break;
case BPF_JGE:
false_reg->umax_value = min(false_reg->umax_value, val - 1);
true_reg->umin_value = max(true_reg->umin_value, val);
break;
case BPF_JSGE:
false_reg->smax_value = min_t(s64, false_reg->smax_value, val - 1);
true_reg->smin_value = max_t(s64, true_reg->smin_value, val);
break;
case BPF_JLE:
false_reg->umin_value = max(false_reg->umin_value, val + 1);
true_reg->umax_value = min(true_reg->umax_value, val);
break;
case BPF_JSLE:
false_reg->smin_value = max_t(s64, false_reg->smin_value, val + 1);
true_reg->smax_value = min_t(s64, true_reg->smax_value, val);
break;
default:
break;
}
__reg_deduce_bounds(false_reg);
__reg_deduce_bounds(true_reg);
/* We might have learned some bits from the bounds. */
__reg_bound_offset(false_reg);
__reg_bound_offset(true_reg);
/* Intersecting with the old var_off might have improved our bounds
* slightly. e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
* then new var_off is (0; 0x7f...fc) which improves our umax.
*/
__update_reg_bounds(false_reg);
__update_reg_bounds(true_reg);
}
/* Same as above, but for the case that dst_reg holds a constant and src_reg is
* the variable reg.
*/
static void reg_set_min_max_inv(struct bpf_reg_state *true_reg,
struct bpf_reg_state *false_reg, u64 val,
u8 opcode)
{
if (__is_pointer_value(false, false_reg))
return;
switch (opcode) {
case BPF_JEQ:
/* If this is false then we know nothing Jon Snow, but if it is
* true then we know for sure.
*/
__mark_reg_known(true_reg, val);
break;
case BPF_JNE:
/* If this is true we know nothing Jon Snow, but if it is false
* we know the value for sure;
*/
__mark_reg_known(false_reg, val);
break;
case BPF_JGT:
true_reg->umax_value = min(true_reg->umax_value, val - 1);
false_reg->umin_value = max(false_reg->umin_value, val);
break;
case BPF_JSGT:
true_reg->smax_value = min_t(s64, true_reg->smax_value, val - 1);
false_reg->smin_value = max_t(s64, false_reg->smin_value, val);
break;
case BPF_JLT:
true_reg->umin_value = max(true_reg->umin_value, val + 1);
false_reg->umax_value = min(false_reg->umax_value, val);
break;
case BPF_JSLT:
true_reg->smin_value = max_t(s64, true_reg->smin_value, val + 1);
false_reg->smax_value = min_t(s64, false_reg->smax_value, val);
break;
case BPF_JGE:
true_reg->umax_value = min(true_reg->umax_value, val);
false_reg->umin_value = max(false_reg->umin_value, val + 1);
break;
case BPF_JSGE:
true_reg->smax_value = min_t(s64, true_reg->smax_value, val);
false_reg->smin_value = max_t(s64, false_reg->smin_value, val + 1);
break;
case BPF_JLE:
true_reg->umin_value = max(true_reg->umin_value, val);
false_reg->umax_value = min(false_reg->umax_value, val - 1);
break;
case BPF_JSLE:
true_reg->smin_value = max_t(s64, true_reg->smin_value, val);
false_reg->smax_value = min_t(s64, false_reg->smax_value, val - 1);
break;
default:
break;
}
__reg_deduce_bounds(false_reg);
__reg_deduce_bounds(true_reg);
/* We might have learned some bits from the bounds. */
__reg_bound_offset(false_reg);
__reg_bound_offset(true_reg);
/* Intersecting with the old var_off might have improved our bounds
* slightly. e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
* then new var_off is (0; 0x7f...fc) which improves our umax.
*/
__update_reg_bounds(false_reg);
__update_reg_bounds(true_reg);
}
/* Regs are known to be equal, so intersect their min/max/var_off */
static void __reg_combine_min_max(struct bpf_reg_state *src_reg,
struct bpf_reg_state *dst_reg)
{
src_reg->umin_value = dst_reg->umin_value = max(src_reg->umin_value,
dst_reg->umin_value);
src_reg->umax_value = dst_reg->umax_value = min(src_reg->umax_value,
dst_reg->umax_value);
src_reg->smin_value = dst_reg->smin_value = max(src_reg->smin_value,
dst_reg->smin_value);
src_reg->smax_value = dst_reg->smax_value = min(src_reg->smax_value,
dst_reg->smax_value);
src_reg->var_off = dst_reg->var_off = tnum_intersect(src_reg->var_off,
dst_reg->var_off);
/* We might have learned new bounds from the var_off. */
__update_reg_bounds(src_reg);
__update_reg_bounds(dst_reg);
/* We might have learned something about the sign bit. */
__reg_deduce_bounds(src_reg);
__reg_deduce_bounds(dst_reg);
/* We might have learned some bits from the bounds. */
__reg_bound_offset(src_reg);
__reg_bound_offset(dst_reg);
/* Intersecting with the old var_off might have improved our bounds
* slightly. e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
* then new var_off is (0; 0x7f...fc) which improves our umax.
*/
__update_reg_bounds(src_reg);
__update_reg_bounds(dst_reg);
}
static void reg_combine_min_max(struct bpf_reg_state *true_src,
struct bpf_reg_state *true_dst,
struct bpf_reg_state *false_src,
struct bpf_reg_state *false_dst,
u8 opcode)
{
switch (opcode) {
case BPF_JEQ:
__reg_combine_min_max(true_src, true_dst);
break;
case BPF_JNE:
__reg_combine_min_max(false_src, false_dst);
break;
}
}
static void mark_map_reg(struct bpf_reg_state *regs, u32 regno, u32 id,
bool is_null)
{
struct bpf_reg_state *reg = &regs[regno];
if (reg->type == PTR_TO_MAP_VALUE_OR_NULL && reg->id == id) {
/* Old offset (both fixed and variable parts) should
* have been known-zero, because we don't allow pointer
* arithmetic on pointers that might be NULL.
*/
if (WARN_ON_ONCE(reg->smin_value || reg->smax_value ||
!tnum_equals_const(reg->var_off, 0) ||
reg->off)) {
__mark_reg_known_zero(reg);
reg->off = 0;
}
if (is_null) {
reg->type = SCALAR_VALUE;
} else if (reg->map_ptr->inner_map_meta) {
reg->type = CONST_PTR_TO_MAP;
reg->map_ptr = reg->map_ptr->inner_map_meta;
} else {
reg->type = PTR_TO_MAP_VALUE;
}
/* We don't need id from this point onwards anymore, thus we
* should better reset it, so that state pruning has chances
* to take effect.
*/
reg->id = 0;
}
}
/* The logic is similar to find_good_pkt_pointers(), both could eventually
* be folded together at some point.
*/
static void mark_map_regs(struct bpf_verifier_state *state, u32 regno,
bool is_null)
{
struct bpf_reg_state *regs = state->regs;
u32 id = regs[regno].id;
int i;
for (i = 0; i < MAX_BPF_REG; i++)
mark_map_reg(regs, i, id, is_null);
for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
if (state->stack_slot_type[i] != STACK_SPILL)
continue;
mark_map_reg(state->spilled_regs, i / BPF_REG_SIZE, id, is_null);
}
}
static int check_cond_jmp_op(struct bpf_verifier_env *env,
struct bpf_insn *insn, int *insn_idx)
{
struct bpf_verifier_state *other_branch, *this_branch = &env->cur_state;
struct bpf_reg_state *regs = this_branch->regs, *dst_reg;
u8 opcode = BPF_OP(insn->code);
int err;
if (opcode > BPF_JSLE) {
verbose("invalid BPF_JMP opcode %x\n", opcode);
return -EINVAL;
}
if (BPF_SRC(insn->code) == BPF_X) {
if (insn->imm != 0) {
verbose("BPF_JMP uses reserved fields\n");
return -EINVAL;
}
/* check src1 operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, insn->src_reg)) {
verbose("R%d pointer comparison prohibited\n",
insn->src_reg);
return -EACCES;
}
} else {
if (insn->src_reg != BPF_REG_0) {
verbose("BPF_JMP uses reserved fields\n");
return -EINVAL;
}
}
/* check src2 operand */
err = check_reg_arg(env, insn->dst_reg, SRC_OP);
if (err)
return err;
dst_reg = &regs[insn->dst_reg];
/* detect if R == 0 where R was initialized to zero earlier */
if (BPF_SRC(insn->code) == BPF_K &&
(opcode == BPF_JEQ || opcode == BPF_JNE) &&
dst_reg->type == SCALAR_VALUE &&
tnum_equals_const(dst_reg->var_off, insn->imm)) {
if (opcode == BPF_JEQ) {
/* if (imm == imm) goto pc+off;
* only follow the goto, ignore fall-through
*/
*insn_idx += insn->off;
return 0;
} else {
/* if (imm != imm) goto pc+off;
* only follow fall-through branch, since
* that's where the program will go
*/
return 0;
}
}
other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx);
if (!other_branch)
return -EFAULT;
/* detect if we are comparing against a constant value so we can adjust
* our min/max values for our dst register.
* this is only legit if both are scalars (or pointers to the same
* object, I suppose, but we don't support that right now), because
* otherwise the different base pointers mean the offsets aren't
* comparable.
*/
if (BPF_SRC(insn->code) == BPF_X) {
if (dst_reg->type == SCALAR_VALUE &&
regs[insn->src_reg].type == SCALAR_VALUE) {
if (tnum_is_const(regs[insn->src_reg].var_off))
reg_set_min_max(&other_branch->regs[insn->dst_reg],
dst_reg, regs[insn->src_reg].var_off.value,
opcode);
else if (tnum_is_const(dst_reg->var_off))
reg_set_min_max_inv(&other_branch->regs[insn->src_reg],
&regs[insn->src_reg],
dst_reg->var_off.value, opcode);
else if (opcode == BPF_JEQ || opcode == BPF_JNE)
/* Comparing for equality, we can combine knowledge */
reg_combine_min_max(&other_branch->regs[insn->src_reg],
&other_branch->regs[insn->dst_reg],
&regs[insn->src_reg],
&regs[insn->dst_reg], opcode);
}
} else if (dst_reg->type == SCALAR_VALUE) {
reg_set_min_max(&other_branch->regs[insn->dst_reg],
dst_reg, insn->imm, opcode);
}
/* detect if R == 0 where R is returned from bpf_map_lookup_elem() */
if (BPF_SRC(insn->code) == BPF_K &&
insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) &&
dst_reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
/* Mark all identical map registers in each branch as either
* safe or unknown depending R == 0 or R != 0 conditional.
*/
mark_map_regs(this_branch, insn->dst_reg, opcode == BPF_JNE);
mark_map_regs(other_branch, insn->dst_reg, opcode == BPF_JEQ);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT &&
dst_reg->type == PTR_TO_PACKET &&
regs[insn->src_reg].type == PTR_TO_PACKET_END) {
/* pkt_data' > pkt_end */
find_good_pkt_pointers(this_branch, dst_reg, false);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT &&
dst_reg->type == PTR_TO_PACKET_END &&
regs[insn->src_reg].type == PTR_TO_PACKET) {
/* pkt_end > pkt_data' */
find_good_pkt_pointers(other_branch, &regs[insn->src_reg], true);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLT &&
dst_reg->type == PTR_TO_PACKET &&
regs[insn->src_reg].type == PTR_TO_PACKET_END) {
/* pkt_data' < pkt_end */
find_good_pkt_pointers(other_branch, dst_reg, true);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLT &&
dst_reg->type == PTR_TO_PACKET_END &&
regs[insn->src_reg].type == PTR_TO_PACKET) {
/* pkt_end < pkt_data' */
find_good_pkt_pointers(this_branch, &regs[insn->src_reg], false);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE &&
dst_reg->type == PTR_TO_PACKET &&
regs[insn->src_reg].type == PTR_TO_PACKET_END) {
/* pkt_data' >= pkt_end */
find_good_pkt_pointers(this_branch, dst_reg, true);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGE &&
dst_reg->type == PTR_TO_PACKET_END &&
regs[insn->src_reg].type == PTR_TO_PACKET) {
/* pkt_end >= pkt_data' */
find_good_pkt_pointers(other_branch, &regs[insn->src_reg], false);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLE &&
dst_reg->type == PTR_TO_PACKET &&
regs[insn->src_reg].type == PTR_TO_PACKET_END) {
/* pkt_data' <= pkt_end */
find_good_pkt_pointers(other_branch, dst_reg, false);
} else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JLE &&
dst_reg->type == PTR_TO_PACKET_END &&
regs[insn->src_reg].type == PTR_TO_PACKET) {
/* pkt_end <= pkt_data' */
find_good_pkt_pointers(this_branch, &regs[insn->src_reg], true);
} else if (is_pointer_value(env, insn->dst_reg)) {
verbose("R%d pointer comparison prohibited\n", insn->dst_reg);
return -EACCES;
}
if (log_level)
print_verifier_state(this_branch);
return 0;
}
/* return the map pointer stored inside BPF_LD_IMM64 instruction */
static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
{
u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
return (struct bpf_map *) (unsigned long) imm64;
}
/* verify BPF_LD_IMM64 instruction */
static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs;
int err;
if (BPF_SIZE(insn->code) != BPF_DW) {
verbose("invalid BPF_LD_IMM insn\n");
return -EINVAL;
}
if (insn->off != 0) {
verbose("BPF_LD_IMM64 uses reserved fields\n");
return -EINVAL;
}
err = check_reg_arg(env, insn->dst_reg, DST_OP);
if (err)
return err;
if (insn->src_reg == 0) {
u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
regs[insn->dst_reg].type = SCALAR_VALUE;
__mark_reg_known(&regs[insn->dst_reg], imm);
return 0;
}
/* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
return 0;
}
static bool may_access_skb(enum bpf_prog_type type)
{
switch (type) {
case BPF_PROG_TYPE_SOCKET_FILTER:
case BPF_PROG_TYPE_SCHED_CLS:
case BPF_PROG_TYPE_SCHED_ACT:
return true;
default:
return false;
}
}
/* verify safety of LD_ABS|LD_IND instructions:
* - they can only appear in the programs where ctx == skb
* - since they are wrappers of function calls, they scratch R1-R5 registers,
* preserve R6-R9, and store return value into R0
*
* Implicit input:
* ctx == skb == R6 == CTX
*
* Explicit input:
* SRC == any register
* IMM == 32-bit immediate
*
* Output:
* R0 - 8/16/32-bit skb data converted to cpu endianness
*/
static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = env->cur_state.regs;
u8 mode = BPF_MODE(insn->code);
int i, err;
if (!may_access_skb(env->prog->type)) {
verbose("BPF_LD_[ABS|IND] instructions not allowed for this program type\n");
return -EINVAL;
}
if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
BPF_SIZE(insn->code) == BPF_DW ||
(mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
verbose("BPF_LD_[ABS|IND] uses reserved fields\n");
return -EINVAL;
}
/* check whether implicit source operand (register R6) is readable */
err = check_reg_arg(env, BPF_REG_6, SRC_OP);
if (err)
return err;
if (regs[BPF_REG_6].type != PTR_TO_CTX) {
verbose("at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
return -EINVAL;
}
if (mode == BPF_IND) {
/* check explicit source operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
}
/* reset caller saved regs to unreadable */
for (i = 0; i < CALLER_SAVED_REGS; i++) {
mark_reg_not_init(regs, caller_saved[i]);
check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
}
/* mark destination R0 register as readable, since it contains
* the value fetched from the packet.
* Already marked as written above.
*/
mark_reg_unknown(regs, BPF_REG_0);
return 0;
}
/* non-recursive DFS pseudo code
* 1 procedure DFS-iterative(G,v):
* 2 label v as discovered
* 3 let S be a stack
* 4 S.push(v)
* 5 while S is not empty
* 6 t <- S.pop()
* 7 if t is what we're looking for:
* 8 return t
* 9 for all edges e in G.adjacentEdges(t) do
* 10 if edge e is already labelled
* 11 continue with the next edge
* 12 w <- G.adjacentVertex(t,e)
* 13 if vertex w is not discovered and not explored
* 14 label e as tree-edge
* 15 label w as discovered
* 16 S.push(w)
* 17 continue at 5
* 18 else if vertex w is discovered
* 19 label e as back-edge
* 20 else
* 21 // vertex w is explored
* 22 label e as forward- or cross-edge
* 23 label t as explored
* 24 S.pop()
*
* convention:
* 0x10 - discovered
* 0x11 - discovered and fall-through edge labelled
* 0x12 - discovered and fall-through and branch edges labelled
* 0x20 - explored
*/
enum {
DISCOVERED = 0x10,
EXPLORED = 0x20,
FALLTHROUGH = 1,
BRANCH = 2,
};
#define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L)
static int *insn_stack; /* stack of insns to process */
static int cur_stack; /* current stack index */
static int *insn_state;
/* t, w, e - match pseudo-code above:
* t - index of current instruction
* w - next instruction
* e - edge
*/
static int push_insn(int t, int w, int e, struct bpf_verifier_env *env)
{
if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
return 0;
if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
return 0;
if (w < 0 || w >= env->prog->len) {
verbose("jump out of range from insn %d to %d\n", t, w);
return -EINVAL;
}
if (e == BRANCH)
/* mark branch target for state pruning */
env->explored_states[w] = STATE_LIST_MARK;
if (insn_state[w] == 0) {
/* tree-edge */
insn_state[t] = DISCOVERED | e;
insn_state[w] = DISCOVERED;
if (cur_stack >= env->prog->len)
return -E2BIG;
insn_stack[cur_stack++] = w;
return 1;
} else if ((insn_state[w] & 0xF0) == DISCOVERED) {
verbose("back-edge from insn %d to %d\n", t, w);
return -EINVAL;
} else if (insn_state[w] == EXPLORED) {
/* forward- or cross-edge */
insn_state[t] = DISCOVERED | e;
} else {
verbose("insn state internal bug\n");
return -EFAULT;
}
return 0;
}
/* non-recursive depth-first-search to detect loops in BPF program
* loop == back-edge in directed graph
*/
static int check_cfg(struct bpf_verifier_env *env)
{
struct bpf_insn *insns = env->prog->insnsi;
int insn_cnt = env->prog->len;
int ret = 0;
int i, t;
insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
if (!insn_state)
return -ENOMEM;
insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
if (!insn_stack) {
kfree(insn_state);
return -ENOMEM;
}
insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
insn_stack[0] = 0; /* 0 is the first instruction */
cur_stack = 1;
peek_stack:
if (cur_stack == 0)
goto check_state;
t = insn_stack[cur_stack - 1];
if (BPF_CLASS(insns[t].code) == BPF_JMP) {
u8 opcode = BPF_OP(insns[t].code);
if (opcode == BPF_EXIT) {
goto mark_explored;
} else if (opcode == BPF_CALL) {
ret = push_insn(t, t + 1, FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
if (t + 1 < insn_cnt)
env->explored_states[t + 1] = STATE_LIST_MARK;
} else if (opcode == BPF_JA) {
if (BPF_SRC(insns[t].code) != BPF_K) {
ret = -EINVAL;
goto err_free;
}
/* unconditional jump with single edge */
ret = push_insn(t, t + insns[t].off + 1,
FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
/* tell verifier to check for equivalent states
* after every call and jump
*/
if (t + 1 < insn_cnt)
env->explored_states[t + 1] = STATE_LIST_MARK;
} else {
/* conditional jump with two edges */
env->explored_states[t] = STATE_LIST_MARK;
ret = push_insn(t, t + 1, FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
}
} else {
/* all other non-branch instructions with single
* fall-through edge
*/
ret = push_insn(t, t + 1, FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
}
mark_explored:
insn_state[t] = EXPLORED;
if (cur_stack-- <= 0) {
verbose("pop stack internal bug\n");
ret = -EFAULT;
goto err_free;
}
goto peek_stack;
check_state:
for (i = 0; i < insn_cnt; i++) {
if (insn_state[i] != EXPLORED) {
verbose("unreachable insn %d\n", i);
ret = -EINVAL;
goto err_free;
}
}
ret = 0; /* cfg looks good */
err_free:
kfree(insn_state);
kfree(insn_stack);
return ret;
}
/* check %cur's range satisfies %old's */
static bool range_within(struct bpf_reg_state *old,
struct bpf_reg_state *cur)
{
return old->umin_value <= cur->umin_value &&
old->umax_value >= cur->umax_value &&
old->smin_value <= cur->smin_value &&
old->smax_value >= cur->smax_value;
}
/* Maximum number of register states that can exist at once */
#define ID_MAP_SIZE (MAX_BPF_REG + MAX_BPF_STACK / BPF_REG_SIZE)
struct idpair {
u32 old;
u32 cur;
};
/* If in the old state two registers had the same id, then they need to have
* the same id in the new state as well. But that id could be different from
* the old state, so we need to track the mapping from old to new ids.
* Once we have seen that, say, a reg with old id 5 had new id 9, any subsequent
* regs with old id 5 must also have new id 9 for the new state to be safe. But
* regs with a different old id could still have new id 9, we don't care about
* that.
* So we look through our idmap to see if this old id has been seen before. If
* so, we require the new id to match; otherwise, we add the id pair to the map.
*/
static bool check_ids(u32 old_id, u32 cur_id, struct idpair *idmap)
{
unsigned int i;
for (i = 0; i < ID_MAP_SIZE; i++) {
if (!idmap[i].old) {
/* Reached an empty slot; haven't seen this id before */
idmap[i].old = old_id;
idmap[i].cur = cur_id;
return true;
}
if (idmap[i].old == old_id)
return idmap[i].cur == cur_id;
}
/* We ran out of idmap slots, which should be impossible */
WARN_ON_ONCE(1);
return false;
}
/* Returns true if (rold safe implies rcur safe) */
static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
struct idpair *idmap)
{
if (!(rold->live & REG_LIVE_READ))
/* explored state didn't use this */
return true;
if (memcmp(rold, rcur, offsetof(struct bpf_reg_state, live)) == 0)
return true;
if (rold->type == NOT_INIT)
/* explored state can't have used this */
return true;
if (rcur->type == NOT_INIT)
return false;
switch (rold->type) {
case SCALAR_VALUE:
if (rcur->type == SCALAR_VALUE) {
/* new val must satisfy old val knowledge */
return range_within(rold, rcur) &&
tnum_in(rold->var_off, rcur->var_off);
} else {
/* We're trying to use a pointer in place of a scalar.
* Even if the scalar was unbounded, this could lead to
* pointer leaks because scalars are allowed to leak
* while pointers are not. We could make this safe in
* special cases if root is calling us, but it's
* probably not worth the hassle.
*/
return false;
}
case PTR_TO_MAP_VALUE:
/* If the new min/max/var_off satisfy the old ones and
* everything else matches, we are OK.
* We don't care about the 'id' value, because nothing
* uses it for PTR_TO_MAP_VALUE (only for ..._OR_NULL)
*/
return memcmp(rold, rcur, offsetof(struct bpf_reg_state, id)) == 0 &&
range_within(rold, rcur) &&
tnum_in(rold->var_off, rcur->var_off);
case PTR_TO_MAP_VALUE_OR_NULL:
/* a PTR_TO_MAP_VALUE could be safe to use as a
* PTR_TO_MAP_VALUE_OR_NULL into the same map.
* However, if the old PTR_TO_MAP_VALUE_OR_NULL then got NULL-
* checked, doing so could have affected others with the same
* id, and we can't check for that because we lost the id when
* we converted to a PTR_TO_MAP_VALUE.
*/
if (rcur->type != PTR_TO_MAP_VALUE_OR_NULL)
return false;
if (memcmp(rold, rcur, offsetof(struct bpf_reg_state, id)))
return false;
/* Check our ids match any regs they're supposed to */
return check_ids(rold->id, rcur->id, idmap);
case PTR_TO_PACKET:
if (rcur->type != PTR_TO_PACKET)
return false;
/* We must have at least as much range as the old ptr
* did, so that any accesses which were safe before are
* still safe. This is true even if old range < old off,
* since someone could have accessed through (ptr - k), or
* even done ptr -= k in a register, to get a safe access.
*/
if (rold->range > rcur->range)
return false;
/* If the offsets don't match, we can't trust our alignment;
* nor can we be sure that we won't fall out of range.
*/
if (rold->off != rcur->off)
return false;
/* id relations must be preserved */
if (rold->id && !check_ids(rold->id, rcur->id, idmap))
return false;
/* new val must satisfy old val knowledge */
return range_within(rold, rcur) &&
tnum_in(rold->var_off, rcur->var_off);
case PTR_TO_CTX:
case CONST_PTR_TO_MAP:
case PTR_TO_STACK:
case PTR_TO_PACKET_END:
/* Only valid matches are exact, which memcmp() above
* would have accepted
*/
default:
/* Don't know what's going on, just say it's not safe */
return false;
}
/* Shouldn't get here; if we do, say it's not safe */
WARN_ON_ONCE(1);
return false;
}
/* compare two verifier states
*
* all states stored in state_list are known to be valid, since
* verifier reached 'bpf_exit' instruction through them
*
* this function is called when verifier exploring different branches of
* execution popped from the state stack. If it sees an old state that has
* more strict register state and more strict stack state then this execution
* branch doesn't need to be explored further, since verifier already
* concluded that more strict state leads to valid finish.
*
* Therefore two states are equivalent if register state is more conservative
* and explored stack state is more conservative than the current one.
* Example:
* explored current
* (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
* (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
*
* In other words if current stack state (one being explored) has more
* valid slots than old one that already passed validation, it means
* the verifier can stop exploring and conclude that current state is valid too
*
* Similarly with registers. If explored state has register type as invalid
* whereas register type in current state is meaningful, it means that
* the current state will reach 'bpf_exit' instruction safely
*/
static bool states_equal(struct bpf_verifier_env *env,
struct bpf_verifier_state *old,
struct bpf_verifier_state *cur)
{
struct idpair *idmap;
bool ret = false;
int i;
idmap = kcalloc(ID_MAP_SIZE, sizeof(struct idpair), GFP_KERNEL);
/* If we failed to allocate the idmap, just say it's not safe */
if (!idmap)
return false;
for (i = 0; i < MAX_BPF_REG; i++) {
if (!regsafe(&old->regs[i], &cur->regs[i], idmap))
goto out_free;
}
for (i = 0; i < MAX_BPF_STACK; i++) {
if (old->stack_slot_type[i] == STACK_INVALID)
continue;
if (old->stack_slot_type[i] != cur->stack_slot_type[i])
/* Ex: old explored (safe) state has STACK_SPILL in
* this stack slot, but current has has STACK_MISC ->
* this verifier states are not equivalent,
* return false to continue verification of this path
*/
goto out_free;
if (i % BPF_REG_SIZE)
continue;
if (old->stack_slot_type[i] != STACK_SPILL)
continue;
if (!regsafe(&old->spilled_regs[i / BPF_REG_SIZE],
&cur->spilled_regs[i / BPF_REG_SIZE],
idmap))
/* when explored and current stack slot are both storing
* spilled registers, check that stored pointers types
* are the same as well.
* Ex: explored safe path could have stored
* (bpf_reg_state) {.type = PTR_TO_STACK, .off = -8}
* but current path has stored:
* (bpf_reg_state) {.type = PTR_TO_STACK, .off = -16}
* such verifier states are not equivalent.
* return false to continue verification of this path
*/
goto out_free;
else
continue;
}
ret = true;
out_free:
kfree(idmap);
return ret;
}
/* A write screens off any subsequent reads; but write marks come from the
* straight-line code between a state and its parent. When we arrive at a
* jump target (in the first iteration of the propagate_liveness() loop),
* we didn't arrive by the straight-line code, so read marks in state must
* propagate to parent regardless of state's write marks.
*/
static bool do_propagate_liveness(const struct bpf_verifier_state *state,
struct bpf_verifier_state *parent)
{
bool writes = parent == state->parent; /* Observe write marks */
bool touched = false; /* any changes made? */
int i;
if (!parent)
return touched;
/* Propagate read liveness of registers... */
BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG);
/* We don't need to worry about FP liveness because it's read-only */
for (i = 0; i < BPF_REG_FP; i++) {
if (parent->regs[i].live & REG_LIVE_READ)
continue;
if (writes && (state->regs[i].live & REG_LIVE_WRITTEN))
continue;
if (state->regs[i].live & REG_LIVE_READ) {
parent->regs[i].live |= REG_LIVE_READ;
touched = true;
}
}
/* ... and stack slots */
for (i = 0; i < MAX_BPF_STACK / BPF_REG_SIZE; i++) {
if (parent->stack_slot_type[i * BPF_REG_SIZE] != STACK_SPILL)
continue;
if (state->stack_slot_type[i * BPF_REG_SIZE] != STACK_SPILL)
continue;
if (parent->spilled_regs[i].live & REG_LIVE_READ)
continue;
if (writes && (state->spilled_regs[i].live & REG_LIVE_WRITTEN))
continue;
if (state->spilled_regs[i].live & REG_LIVE_READ) {
parent->spilled_regs[i].live |= REG_LIVE_READ;
touched = true;
}
}
return touched;
}
/* "parent" is "a state from which we reach the current state", but initially
* it is not the state->parent (i.e. "the state whose straight-line code leads
* to the current state"), instead it is the state that happened to arrive at
* a (prunable) equivalent of the current state. See comment above
* do_propagate_liveness() for consequences of this.
* This function is just a more efficient way of calling mark_reg_read() or
* mark_stack_slot_read() on each reg in "parent" that is read in "state",
* though it requires that parent != state->parent in the call arguments.
*/
static void propagate_liveness(const struct bpf_verifier_state *state,
struct bpf_verifier_state *parent)
{
while (do_propagate_liveness(state, parent)) {
/* Something changed, so we need to feed those changes onward */
state = parent;
parent = state->parent;
}
}
static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
{
struct bpf_verifier_state_list *new_sl;
struct bpf_verifier_state_list *sl;
int i;
sl = env->explored_states[insn_idx];
if (!sl)
/* this 'insn_idx' instruction wasn't marked, so we will not
* be doing state search here
*/
return 0;
while (sl != STATE_LIST_MARK) {
if (states_equal(env, &sl->state, &env->cur_state)) {
/* reached equivalent register/stack state,
* prune the search.
* Registers read by the continuation are read by us.
* If we have any write marks in env->cur_state, they
* will prevent corresponding reads in the continuation
* from reaching our parent (an explored_state). Our
* own state will get the read marks recorded, but
* they'll be immediately forgotten as we're pruning
* this state and will pop a new one.
*/
propagate_liveness(&sl->state, &env->cur_state);
return 1;
}
sl = sl->next;
}
/* there were no equivalent states, remember current one.
* technically the current state is not proven to be safe yet,
* but it will either reach bpf_exit (which means it's safe) or
* it will be rejected. Since there are no loops, we won't be
* seeing this 'insn_idx' instruction again on the way to bpf_exit
*/
new_sl = kmalloc(sizeof(struct bpf_verifier_state_list), GFP_USER);
if (!new_sl)
return -ENOMEM;
/* add new state to the head of linked list */
memcpy(&new_sl->state, &env->cur_state, sizeof(env->cur_state));
new_sl->next = env->explored_states[insn_idx];
env->explored_states[insn_idx] = new_sl;
/* connect new state to parentage chain */
env->cur_state.parent = &new_sl->state;
/* clear write marks in current state: the writes we did are not writes
* our child did, so they don't screen off its reads from us.
* (There are no read marks in current state, because reads always mark
* their parent and current state never has children yet. Only
* explored_states can get read marks.)
*/
for (i = 0; i < BPF_REG_FP; i++)
env->cur_state.regs[i].live = REG_LIVE_NONE;
for (i = 0; i < MAX_BPF_STACK / BPF_REG_SIZE; i++)
if (env->cur_state.stack_slot_type[i * BPF_REG_SIZE] == STACK_SPILL)
env->cur_state.spilled_regs[i].live = REG_LIVE_NONE;
return 0;
}
static int ext_analyzer_insn_hook(struct bpf_verifier_env *env,
int insn_idx, int prev_insn_idx)
{
if (!env->analyzer_ops || !env->analyzer_ops->insn_hook)
return 0;
return env->analyzer_ops->insn_hook(env, insn_idx, prev_insn_idx);
}
static int do_check(struct bpf_verifier_env *env)
{
struct bpf_verifier_state *state = &env->cur_state;
struct bpf_insn *insns = env->prog->insnsi;
struct bpf_reg_state *regs = state->regs;
int insn_cnt = env->prog->len;
int insn_idx, prev_insn_idx = 0;
int insn_processed = 0;
bool do_print_state = false;
init_reg_state(regs);
state->parent = NULL;
insn_idx = 0;
for (;;) {
struct bpf_insn *insn;
u8 class;
int err;
if (insn_idx >= insn_cnt) {
verbose("invalid insn idx %d insn_cnt %d\n",
insn_idx, insn_cnt);
return -EFAULT;
}
insn = &insns[insn_idx];
class = BPF_CLASS(insn->code);
if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
verbose("BPF program is too large. Processed %d insn\n",
insn_processed);
return -E2BIG;
}
err = is_state_visited(env, insn_idx);
if (err < 0)
return err;
if (err == 1) {
/* found equivalent state, can prune the search */
if (log_level) {
if (do_print_state)
verbose("\nfrom %d to %d: safe\n",
prev_insn_idx, insn_idx);
else
verbose("%d: safe\n", insn_idx);
}
goto process_bpf_exit;
}
if (need_resched())
cond_resched();
if (log_level > 1 || (log_level && do_print_state)) {
if (log_level > 1)
verbose("%d:", insn_idx);
else
verbose("\nfrom %d to %d:",
prev_insn_idx, insn_idx);
print_verifier_state(&env->cur_state);
do_print_state = false;
}
if (log_level) {
verbose("%d: ", insn_idx);
print_bpf_insn(env, insn);
}
err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx);
if (err)
return err;
env->insn_aux_data[insn_idx].seen = true;
if (class == BPF_ALU || class == BPF_ALU64) {
err = check_alu_op(env, insn);
if (err)
return err;
} else if (class == BPF_LDX) {
enum bpf_reg_type *prev_src_type, src_reg_type;
/* check for reserved fields is already done */
/* check src operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
if (err)
return err;
src_reg_type = regs[insn->src_reg].type;
/* check that memory (src_reg + off) is readable,
* the state of dst_reg will be updated by this func
*/
err = check_mem_access(env, insn_idx, insn->src_reg, insn->off,
BPF_SIZE(insn->code), BPF_READ,
insn->dst_reg, false);
if (err)
return err;
prev_src_type = &env->insn_aux_data[insn_idx].ptr_type;
if (*prev_src_type == NOT_INIT) {
/* saw a valid insn
* dst_reg = *(u32 *)(src_reg + off)
* save type to validate intersecting paths
*/
*prev_src_type = src_reg_type;
} else if (src_reg_type != *prev_src_type &&
(src_reg_type == PTR_TO_CTX ||
*prev_src_type == PTR_TO_CTX)) {
/* ABuser program is trying to use the same insn
* dst_reg = *(u32*) (src_reg + off)
* with different pointer types:
* src_reg == ctx in one branch and