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/*
* Copyright (c) 2016 Apple Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
*
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_END@
*/
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <vm/vm_map.h>
#include <kern/assert.h>
#include <kern/cpu_data.h>
#include <kern/backtrace.h>
#include <machine/machine_routines.h>
#include <kern/locks.h>
#include <kern/simple_lock.h>
#include <kern/debug.h>
#include <kern/kalloc.h>
#include <kern/zalloc.h>
#include <mach/mach_vm.h>
#include <mach/mach_types.h>
#include <mach/vm_param.h>
#include <mach/machine/vm_param.h>
#include <libkern/libkern.h>
#include <libkern/OSAtomic.h>
#include <libkern/kernel_mach_header.h>
#include <sys/queue.h>
#include <sys/sysctl.h>
#include <kern/thread.h>
#include <machine/atomic.h>
#include <kasan.h>
#include <kasan_internal.h>
#include <memintrinsics.h>
const uintptr_t __asan_shadow_memory_dynamic_address = KASAN_SHIFT;
static unsigned kexts_loaded;
unsigned shadow_pages_total;
unsigned shadow_pages_used;
vm_offset_t kernel_vbase;
vm_offset_t kernel_vtop;
static unsigned kasan_enabled;
static unsigned quarantine_enabled;
static unsigned enabled_checks = TYPE_ALL; /* bitmask of enabled checks */
static unsigned report_ignored; /* issue non-fatal report for disabled/blacklisted checks */
static unsigned free_yield = 0; /* ms yield after each free */
/* forward decls */
static void kasan_crash_report(uptr p, uptr width, access_t access, violation_t reason);
static void kasan_log_report(uptr p, uptr width, access_t access, violation_t reason);
/* imported osfmk functions */
extern vm_offset_t ml_stack_base(void);
extern vm_size_t ml_stack_size(void);
/*
* unused: expected to be called, but (currently) does nothing
*/
#define UNUSED_ABI(func, ...) \
_Pragma("clang diagnostic push") \
_Pragma("clang diagnostic ignored \"-Wunused-parameter\"") \
void func(__VA_ARGS__); \
void func(__VA_ARGS__) {}; \
_Pragma("clang diagnostic pop") \
static const size_t BACKTRACE_BITS = 4;
static const size_t BACKTRACE_MAXFRAMES = (1UL << BACKTRACE_BITS) - 1;
decl_simple_lock_data(, kasan_vm_lock);
static thread_t kasan_lock_holder;
/*
* kasan is called from the interrupt path, so we need to disable interrupts to
* ensure atomicity manipulating the global objects
*/
void
kasan_lock(boolean_t *b)
{
*b = ml_set_interrupts_enabled(false);
simple_lock(&kasan_vm_lock);
kasan_lock_holder = current_thread();
}
void
kasan_unlock(boolean_t b)
{
kasan_lock_holder = THREAD_NULL;
simple_unlock(&kasan_vm_lock);
ml_set_interrupts_enabled(b);
}
/* Return true if 'thread' holds the kasan lock. Only safe if 'thread' == current
* thread */
bool
kasan_lock_held(thread_t thread)
{
return thread && thread == kasan_lock_holder;
}
static inline bool
kasan_check_enabled(access_t access)
{
return kasan_enabled && (enabled_checks & access) && !kasan_is_blacklisted(access);
}
static inline bool
kasan_poison_active(uint8_t flags)
{
switch (flags) {
case ASAN_GLOBAL_RZ:
return kasan_check_enabled(TYPE_POISON_GLOBAL);
case ASAN_HEAP_RZ:
case ASAN_HEAP_LEFT_RZ:
case ASAN_HEAP_RIGHT_RZ:
case ASAN_HEAP_FREED:
return kasan_check_enabled(TYPE_POISON_HEAP);
default:
return true;
};
}
/*
* poison redzones in the shadow map
*/
void NOINLINE
kasan_poison(vm_offset_t base, vm_size_t size, vm_size_t leftrz, vm_size_t rightrz, uint8_t flags)
{
uint8_t *shadow = SHADOW_FOR_ADDRESS(base);
uint8_t partial = size & 0x07;
vm_size_t total = leftrz + size + rightrz;
vm_size_t i = 0;
/* base must be 8-byte aligned */
/* any left redzone must be a multiple of 8 */
/* total region must cover 8-byte multiple */
assert((base & 0x07) == 0);
assert((leftrz & 0x07) == 0);
assert((total & 0x07) == 0);
if (!kasan_enabled || !kasan_poison_active(flags)) {
return;
}
leftrz /= 8;
size /= 8;
total /= 8;
uint8_t l_flags = flags;
uint8_t r_flags = flags;
if (flags == ASAN_STACK_RZ) {
l_flags = ASAN_STACK_LEFT_RZ;
r_flags = ASAN_STACK_RIGHT_RZ;
} else if (flags == ASAN_HEAP_RZ) {
l_flags = ASAN_HEAP_LEFT_RZ;
r_flags = ASAN_HEAP_RIGHT_RZ;
}
/*
* poison the redzones and unpoison the valid bytes
*/
for (; i < leftrz; i++) {
shadow[i] = l_flags;
}
for (; i < leftrz + size; i++) {
shadow[i] = ASAN_VALID; /* XXX: should not be necessary */
}
if (partial && (i < total)) {
shadow[i] = partial;
i++;
}
for (; i < total; i++) {
shadow[i] = r_flags;
}
}
void
kasan_poison_range(vm_offset_t base, vm_size_t size, uint8_t flags)
{
/* base must be 8-byte aligned */
/* total region must cover 8-byte multiple */
assert((base & 0x07) == 0);
assert((size & 0x07) == 0);
kasan_poison(base, 0, 0, size, flags);
}
void NOINLINE
kasan_unpoison(void *base, vm_size_t size)
{
kasan_poison((vm_offset_t)base, size, 0, 0, 0);
}
void NOINLINE
kasan_unpoison_stack(vm_offset_t base, vm_size_t size)
{
assert(base);
assert(size);
/* align base and size to 8 bytes */
vm_offset_t align = base & 0x7;
base -= align;
size += align;
size = (size + 7) & ~0x7;
kasan_unpoison((void *)base, size);
}
/*
* write junk into the redzones
*/
static void NOINLINE
kasan_rz_clobber(vm_offset_t base, vm_size_t size, vm_size_t leftrz, vm_size_t rightrz)
{
#if KASAN_DEBUG
vm_size_t i;
const uint8_t deadbeef[] = { 0xde, 0xad, 0xbe, 0xef };
const uint8_t c0ffee[] = { 0xc0, 0xff, 0xee, 0xc0 };
uint8_t *buf = (uint8_t *)base;
/* base must be 8-byte aligned */
/* any left redzone must be a multiple of 8 */
/* total region must cover 8-byte multiple */
assert((base & 0x07) == 0);
assert((leftrz & 0x07) == 0);
assert(((size + leftrz + rightrz) & 0x07) == 0);
for (i = 0; i < leftrz; i++) {
buf[i] = deadbeef[i % 4];
}
for (i = 0; i < rightrz; i++) {
buf[i + size + leftrz] = c0ffee[i % 4];
}
#else
(void)base;
(void)size;
(void)leftrz;
(void)rightrz;
#endif
}
/*
* Report a violation that may be disabled and/or blacklisted. This can only be
* called for dynamic checks (i.e. where the fault is recoverable). Use
* kasan_crash_report() for static (unrecoverable) violations.
*
* access: what we were trying to do when the violation occured
* reason: what failed about the access
*/
static void
kasan_violation(uintptr_t addr, size_t size, access_t access, violation_t reason)
{
assert(__builtin_popcount(access) == 1);
if (!kasan_check_enabled(access)) {
if (report_ignored) {
kasan_log_report(addr, size, access, reason);
}
return;
}
kasan_crash_report(addr, size, access, reason);
}
void NOINLINE
kasan_check_range(const void *x, size_t sz, access_t access)
{
uintptr_t invalid;
uintptr_t ptr = (uintptr_t)x;
if (kasan_range_poisoned(ptr, sz, &invalid)) {
size_t remaining = sz - (invalid - ptr);
kasan_violation(invalid, remaining, access, 0);
}
}
/*
* Return true if [base, base+sz) is unpoisoned or has given shadow value.
*/
bool
kasan_check_shadow(vm_address_t base, vm_size_t sz, uint8_t shadow)
{
sz -= 8 - (base % 8);
base += 8 - (base % 8);
vm_address_t end = base + sz;
while (base < end) {
uint8_t *sh = SHADOW_FOR_ADDRESS(base);
if (*sh && *sh != shadow) {
return false;
}
base += 8;
}
return true;
}
/*
*
* KASAN violation reporting
*
*/
static const char *
access_str(access_t type)
{
if (type & TYPE_READ) {
return "load from";
} else if (type & TYPE_WRITE) {
return "store to";
} else if (type & TYPE_FREE) {
return "free of";
} else {
return "access of";
}
}
static const char *shadow_strings[] = {
[ASAN_VALID] = "VALID",
[ASAN_PARTIAL1] = "PARTIAL1",
[ASAN_PARTIAL2] = "PARTIAL2",
[ASAN_PARTIAL3] = "PARTIAL3",
[ASAN_PARTIAL4] = "PARTIAL4",
[ASAN_PARTIAL5] = "PARTIAL5",
[ASAN_PARTIAL6] = "PARTIAL6",
[ASAN_PARTIAL7] = "PARTIAL7",
[ASAN_STACK_LEFT_RZ] = "STACK_LEFT_RZ",
[ASAN_STACK_MID_RZ] = "STACK_MID_RZ",
[ASAN_STACK_RIGHT_RZ] = "STACK_RIGHT_RZ",
[ASAN_STACK_FREED] = "STACK_FREED",
[ASAN_STACK_OOSCOPE] = "STACK_OOSCOPE",
[ASAN_GLOBAL_RZ] = "GLOBAL_RZ",
[ASAN_HEAP_LEFT_RZ] = "HEAP_LEFT_RZ",
[ASAN_HEAP_RIGHT_RZ] = "HEAP_RIGHT_RZ",
[ASAN_HEAP_FREED] = "HEAP_FREED",
[0xff] = NULL
};
#define CRASH_CONTEXT_BEFORE 5
#define CRASH_CONTEXT_AFTER 5
static size_t
kasan_shadow_crashlog(uptr p, char *buf, size_t len)
{
int i,j;
size_t n = 0;
int before = CRASH_CONTEXT_BEFORE;
int after = CRASH_CONTEXT_AFTER;
uptr shadow = (uptr)SHADOW_FOR_ADDRESS(p);
uptr shadow_p = shadow;
uptr shadow_page = vm_map_round_page(shadow_p, HW_PAGE_MASK);
/* rewind to start of context block */
shadow &= ~((uptr)0xf);
shadow -= 16 * before;
n += snprintf(buf+n, len-n,
" Shadow 0 1 2 3 4 5 6 7 8 9 a b c d e f\n");
for (i = 0; i < 1 + before + after; i++, shadow += 16) {
if ((vm_map_round_page(shadow, HW_PAGE_MASK) != shadow_page) && !kasan_is_shadow_mapped(shadow)) {
/* avoid unmapped shadow when crossing page boundaries */
continue;
}
n += snprintf(buf+n, len-n, " %16lx:", shadow);
char *left = " ";
char *right;
for (j = 0; j < 16; j++) {
uint8_t *x = (uint8_t *)(shadow + j);
right = " ";
if ((uptr)x == shadow_p) {
left = "[";
right = "]";
} else if ((uptr)(x + 1) == shadow_p) {
right = "";
}
n += snprintf(buf+n, len-n, "%s%02x%s", left, (unsigned)*x, right);
left = "";
}
n += snprintf(buf+n, len-n, "\n");
}
n += snprintf(buf+n, len-n, "\n");
return n;
}
static void
kasan_report_internal(uptr p, uptr width, access_t access, violation_t reason, bool dopanic)
{
const size_t len = 4096;
static char buf[len];
size_t n = 0;
uint8_t *shadow_ptr = SHADOW_FOR_ADDRESS(p);
uint8_t shadow_type = *shadow_ptr;
const char *shadow_str = shadow_strings[shadow_type];
if (!shadow_str) {
shadow_str = "<invalid>";
}
buf[0] = '\0';
if (reason == REASON_MOD_OOB || reason == REASON_BAD_METADATA) {
n += snprintf(buf+n, len-n, "KASan: free of corrupted/invalid object %#lx\n", p);
} else if (reason == REASON_MOD_AFTER_FREE) {
n += snprintf(buf+n, len-n, "KASan: UaF of quarantined object %#lx\n", p);
} else {
n += snprintf(buf+n, len-n, "KASan: invalid %lu-byte %s %#lx [%s]\n",
width, access_str(access), p, shadow_str);
}
n += kasan_shadow_crashlog(p, buf+n, len-n);
if (dopanic) {
panic("%s", buf);
} else {
printf("%s", buf);
}
}
static void NOINLINE OS_NORETURN
kasan_crash_report(uptr p, uptr width, access_t access, violation_t reason)
{
kasan_handle_test();
kasan_report_internal(p, width, access, reason, true);
__builtin_unreachable(); /* we cant handle this returning anyway */
}
static void
kasan_log_report(uptr p, uptr width, access_t access, violation_t reason)
{
const size_t len = 256;
char buf[len];
size_t l = 0;
uint32_t nframes = 14;
uintptr_t frames[nframes];
uintptr_t *bt = frames;
kasan_report_internal(p, width, access, reason, false);
/*
* print a backtrace
*/
nframes = backtrace_frame(bt, nframes, __builtin_frame_address(0)); /* ignore current frame */
buf[0] = '\0';
l += snprintf(buf+l, len-l, "Backtrace: ");
for (uint32_t i = 0; i < nframes; i++) {
l += snprintf(buf+l, len-l, "%lx,", VM_KERNEL_UNSLIDE(bt[i]));
}
l += snprintf(buf+l, len-l, "\n");
printf("%s", buf);
}
#define REPORT_DECLARE(n) \
void OS_NORETURN __asan_report_load##n(uptr p) { kasan_crash_report(p, n, TYPE_LOAD, 0); } \
void OS_NORETURN __asan_report_store##n(uptr p) { kasan_crash_report(p, n, TYPE_STORE, 0); } \
void UNSUPPORTED_API(__asan_report_exp_load##n, uptr a, int32_t b); \
void UNSUPPORTED_API(__asan_report_exp_store##n, uptr a, int32_t b);
REPORT_DECLARE(1)
REPORT_DECLARE(2)
REPORT_DECLARE(4)
REPORT_DECLARE(8)
REPORT_DECLARE(16)
void OS_NORETURN __asan_report_load_n(uptr p, unsigned long sz) { kasan_crash_report(p, sz, TYPE_LOAD, 0); }
void OS_NORETURN __asan_report_store_n(uptr p, unsigned long sz) { kasan_crash_report(p, sz, TYPE_STORE, 0); }
/* unpoison the current stack */
void NOINLINE
kasan_unpoison_curstack(bool whole_stack)
{
uintptr_t base = ml_stack_base();
size_t sz = ml_stack_size();
uintptr_t cur = (uintptr_t)&base;
if (whole_stack) {
cur = base;
}
if (cur >= base && cur < base + sz) {
/* unpoison from current stack depth to the top */
size_t unused = cur - base;
kasan_unpoison_stack(cur, sz - unused);
}
}
void NOINLINE
__asan_handle_no_return(void)
{
kasan_unpoison_curstack(false);
/*
* No need to free any fakestack objects because they must stay alive until
* we drop the real stack, at which point we can drop the entire fakestack
* anyway.
*/
}
bool NOINLINE
kasan_range_poisoned(vm_offset_t base, vm_size_t size, vm_offset_t *first_invalid)
{
uint8_t *shadow;
vm_size_t i;
if (!kasan_enabled) {
return false;
}
size += base & 0x07;
base &= ~(vm_offset_t)0x07;
shadow = SHADOW_FOR_ADDRESS(base);
vm_size_t limit = (size + 7) / 8;
/* XXX: to make debugging easier, catch unmapped shadow here */
for (i = 0; i < limit; i++, size -= 8) {
assert(size > 0);
uint8_t s = shadow[i];
if (s == 0 || (size < 8 && s >= size && s <= 7)) {
/* valid */
} else {
goto fail;
}
}
return false;
fail:
if (first_invalid) {
/* XXX: calculate the exact first byte that failed */
*first_invalid = base + i*8;
}
return true;
}
static void NOINLINE
kasan_init_globals(vm_offset_t base, vm_size_t size)
{
struct asan_global *glob = (struct asan_global *)base;
struct asan_global *glob_end = (struct asan_global *)(base + size);
for (; glob < glob_end; glob++) {
/* handle one global */
kasan_poison(glob->addr, glob->size, 0, glob->size_with_redzone - glob->size, ASAN_GLOBAL_RZ);
}
}
void NOINLINE
kasan_load_kext(vm_offset_t base, vm_size_t __unused size, const void *bundleid)
{
unsigned long sectsz;
void *sect;
#if KASAN_DYNAMIC_BLACKLIST
kasan_dybl_load_kext(base, bundleid);
#endif
/* find the kasan globals segment/section */
sect = getsectdatafromheader((void *)base, KASAN_GLOBAL_SEGNAME, KASAN_GLOBAL_SECTNAME, &sectsz);
if (sect) {
kasan_init_globals((vm_address_t)sect, (vm_size_t)sectsz);
kexts_loaded++;
}
}
void NOINLINE
kasan_unload_kext(vm_offset_t base, vm_size_t size)
{
unsigned long sectsz;
void *sect;
/* find the kasan globals segment/section */
sect = getsectdatafromheader((void *)base, KASAN_GLOBAL_SEGNAME, KASAN_GLOBAL_SECTNAME, &sectsz);
if (sect) {
kasan_unpoison((void *)base, size);
kexts_loaded--;
}
#if KASAN_DYNAMIC_BLACKLIST
kasan_dybl_unload_kext(base);
#endif
}
/*
* Turn off as much as possible for panic path etc. There's no way to turn it back
* on.
*/
void NOINLINE
kasan_disable(void)
{
__asan_option_detect_stack_use_after_return = 0;
fakestack_enabled = 0;
kasan_enabled = 0;
quarantine_enabled = 0;
enabled_checks = 0;
}
static void NOINLINE
kasan_init_xnu_globals(void)
{
const char *seg = KASAN_GLOBAL_SEGNAME;
const char *sect = KASAN_GLOBAL_SECTNAME;
unsigned long _size;
vm_offset_t globals;
vm_size_t size;
kernel_mach_header_t *header = (kernel_mach_header_t *)&_mh_execute_header;
if (!header) {
printf("KASan: failed to find kernel mach header\n");
printf("KASan: redzones for globals not poisoned\n");
return;
}
globals = (vm_offset_t)getsectdatafromheader(header, seg, sect, &_size);
if (!globals) {
printf("KASan: failed to find segment %s section %s\n", seg, sect);
printf("KASan: redzones for globals not poisoned\n");
return;
}
size = (vm_size_t)_size;
printf("KASan: found (%s,%s) at %#lx + %lu\n", seg, sect, globals, size);
printf("KASan: poisoning redzone for %lu globals\n", size / sizeof(struct asan_global));
kasan_init_globals(globals, size);
}
void NOINLINE
kasan_late_init(void)
{
#if KASAN_DYNAMIC_BLACKLIST
kasan_init_dybl();
#endif
kasan_init_fakestack();
kasan_init_xnu_globals();
}
void NOINLINE
kasan_notify_stolen(vm_offset_t top)
{
kasan_map_shadow(kernel_vtop, top - kernel_vtop, false);
}
static void NOINLINE
kasan_debug_touch_mappings(vm_offset_t base, vm_size_t sz)
{
#if KASAN_DEBUG
vm_size_t i;
uint8_t tmp1, tmp2;
/* Hit every byte in the shadow map. Don't write due to the zero mappings. */
for (i = 0; i < sz; i += sizeof(uint64_t)) {
vm_offset_t addr = base + i;
uint8_t *x = SHADOW_FOR_ADDRESS(addr);
tmp1 = *x;
asm volatile("" ::: "memory");
tmp2 = *x;
asm volatile("" ::: "memory");
assert(tmp1 == tmp2);
}
#else
(void)base;
(void)sz;
#endif
}
void NOINLINE
kasan_init(void)
{
unsigned arg;
simple_lock_init(&kasan_vm_lock, 0);
/* Map all of the kernel text and data */
kasan_map_shadow(kernel_vbase, kernel_vtop - kernel_vbase, false);
kasan_arch_init();
/*
* handle KASan boot-args
*/
if (PE_parse_boot_argn("kasan.checks", &arg, sizeof(arg))) {
enabled_checks = arg;
}
if (PE_parse_boot_argn("kasan", &arg, sizeof(arg))) {
if (arg & KASAN_ARGS_FAKESTACK) {
fakestack_enabled = 1;
}
if (arg & KASAN_ARGS_REPORTIGNORED) {
report_ignored = 1;
}
if (arg & KASAN_ARGS_NODYCHECKS) {
enabled_checks &= ~TYPE_DYNAMIC;
}
if (arg & KASAN_ARGS_NOPOISON_HEAP) {
enabled_checks &= ~TYPE_POISON_HEAP;
}
if (arg & KASAN_ARGS_NOPOISON_GLOBAL) {
enabled_checks &= ~TYPE_POISON_GLOBAL;
}
}
if (PE_parse_boot_argn("kasan.free_yield_ms", &arg, sizeof(arg))) {
free_yield = arg;
}
/* kasan.bl boot-arg handled in kasan_init_dybl() */
quarantine_enabled = 1;
kasan_enabled = 1;
}
static void NOINLINE
kasan_notify_address_internal(vm_offset_t address, vm_size_t size, bool is_zero)
{
assert(address < VM_MAX_KERNEL_ADDRESS);
if (!kasan_enabled) {
return;
}
if (address < VM_MIN_KERNEL_AND_KEXT_ADDRESS) {
/* only map kernel addresses */
return;
}
if (!size) {
/* nothing to map */
return;
}
boolean_t flags;
kasan_lock(&flags);
kasan_map_shadow(address, size, is_zero);
kasan_unlock(flags);
kasan_debug_touch_mappings(address, size);
}
void
kasan_notify_address(vm_offset_t address, vm_size_t size)
{
kasan_notify_address_internal(address, size, false);
}
/*
* Allocate read-only, all-zeros shadow for memory that can never be poisoned
*/
void
kasan_notify_address_nopoison(vm_offset_t address, vm_size_t size)
{
kasan_notify_address_internal(address, size, true);
}
/*
*
* allocator hooks
*
*/
struct kasan_alloc_header {
uint16_t magic;
uint16_t crc;
uint32_t alloc_size;
uint32_t user_size;
struct {
uint32_t left_rz : 32 - BACKTRACE_BITS;
uint32_t frames : BACKTRACE_BITS;
};
};
_Static_assert(sizeof(struct kasan_alloc_header) <= KASAN_GUARD_SIZE, "kasan alloc header exceeds guard size");
struct kasan_alloc_footer {
uint32_t backtrace[0];
};
_Static_assert(sizeof(struct kasan_alloc_footer) <= KASAN_GUARD_SIZE, "kasan alloc footer exceeds guard size");
#define LIVE_XOR ((uint16_t)0x3a65)
#define FREE_XOR ((uint16_t)0xf233)
static uint16_t
magic_for_addr(vm_offset_t addr, uint16_t magic_xor)
{
uint16_t magic = addr & 0xFFFF;
magic ^= (addr >> 16) & 0xFFFF;
magic ^= (addr >> 32) & 0xFFFF;
magic ^= (addr >> 48) & 0xFFFF;
magic ^= magic_xor;
return magic;
}
static struct kasan_alloc_header *
header_for_user_addr(vm_offset_t addr)
{
return (void *)(addr - sizeof(struct kasan_alloc_header));
}
static struct kasan_alloc_footer *
footer_for_user_addr(vm_offset_t addr, vm_size_t *size)
{
struct kasan_alloc_header *h = header_for_user_addr(addr);
vm_size_t rightrz = h->alloc_size - h->user_size - h->left_rz;
*size = rightrz;
return (void *)(addr + h->user_size);
}
/*
* size: user-requested allocation size
* ret: minimum size for the real allocation
*/
vm_size_t
kasan_alloc_resize(vm_size_t size)
{
vm_size_t tmp;
if (os_add_overflow(size, 4 * PAGE_SIZE, &tmp)) {
panic("allocation size overflow (%lu)", size);
}
/* add left and right redzones */
size += KASAN_GUARD_PAD;
/* ensure the final allocation is an 8-byte multiple */
size += 8 - (size % 8);
return size;
}
extern vm_offset_t vm_kernel_slid_base;
static vm_size_t
kasan_alloc_bt(uint32_t *ptr, vm_size_t sz, vm_size_t skip)
{
uintptr_t buf[BACKTRACE_MAXFRAMES];
uintptr_t *bt = buf;
sz /= sizeof(uint32_t);
vm_size_t frames = sz;
if (frames > 0) {
frames = min(frames + skip, BACKTRACE_MAXFRAMES);
frames = backtrace(bt, frames);
while (frames > sz && skip > 0) {
bt++;
frames--;
skip--;
}
/* only store the offset from kernel base, and cram that into 32
* bits */
for (vm_size_t i = 0; i < frames; i++) {
ptr[i] = (uint32_t)(bt[i] - vm_kernel_slid_base);
}
}
return frames;
}
/* addr: user address of allocation */
static uint16_t
kasan_alloc_crc(vm_offset_t addr)
{
struct kasan_alloc_header *h = header_for_user_addr(addr);
vm_size_t rightrz = h->alloc_size - h->user_size - h->left_rz;
uint16_t crc_orig = h->crc;
h->crc = 0;
uint16_t crc = 0;
crc = __nosan_crc16(crc, (void *)(addr - h->left_rz), h->left_rz);
crc = __nosan_crc16(crc, (void *)(addr + h->user_size), rightrz);
h->crc = crc_orig;
return crc;
}
/*
* addr: base address of full allocation (including redzones)
* size: total size of allocation (include redzones)
* req: user-requested allocation size
* lrz: size of the left redzone in bytes
* ret: address of usable allocation
*/
vm_address_t
kasan_alloc(vm_offset_t addr, vm_size_t size, vm_size_t req, vm_size_t leftrz)
{
if (!addr) {
return 0;
}
assert(size > 0);
assert((addr % 8) == 0);
assert((size % 8) == 0);
vm_size_t rightrz = size - req - leftrz;
kasan_poison(addr, req, leftrz, rightrz, ASAN_HEAP_RZ);
kasan_rz_clobber(addr, req, leftrz, rightrz);
addr += leftrz;
/* stash the allocation sizes in the left redzone */
struct kasan_alloc_header *h = header_for_user_addr(addr);
h->magic = magic_for_addr(addr, LIVE_XOR);
h->left_rz = leftrz;
h->alloc_size = size;
h->user_size = req;
/* ... and a backtrace in the right redzone */
vm_size_t fsize;
struct kasan_alloc_footer *f = footer_for_user_addr(addr, &fsize);
h->frames = kasan_alloc_bt(f->backtrace, fsize, 2);
/* checksum the whole object, minus the user part */
h->crc = kasan_alloc_crc(addr);
return addr;
}
/*
* addr: user pointer
* size: returns full original allocation size
* ret: original allocation ptr
*/
vm_address_t
kasan_dealloc(vm_offset_t addr, vm_size_t *size)
{
assert(size && addr);
struct kasan_alloc_header *h = header_for_user_addr(addr);
*size = h->alloc_size;
return addr - h->left_rz;
}
/*
* return the original user-requested allocation size
* addr: user alloc pointer
*/
vm_size_t
kasan_user_size(vm_offset_t addr)
{
struct kasan_alloc_header *h = header_for_user_addr(addr);
assert(h->magic == magic_for_addr(addr, LIVE_XOR));
return h->user_size;
}
/*
* Verify that `addr' (user pointer) is a valid allocation of `type'
*/
void
kasan_check_free(vm_offset_t addr, vm_size_t size, unsigned heap_type)
{
struct kasan_alloc_header *h = header_for_user_addr(addr);
/* map heap type to an internal access type */
access_t type = heap_type == KASAN_HEAP_KALLOC ? TYPE_KFREE :
heap_type == KASAN_HEAP_ZALLOC ? TYPE_ZFREE :
heap_type == KASAN_HEAP_FAKESTACK ? TYPE_FSFREE : 0;
/* check the magic and crc match */
if (h->magic != magic_for_addr(addr, LIVE_XOR)) {
kasan_violation(addr, size, type, REASON_BAD_METADATA);
}
if (h->crc != kasan_alloc_crc(addr)) {
kasan_violation(addr, size, type, REASON_MOD_OOB);
}
/* check the freed size matches what we recorded at alloc time */
if (h->user_size != size) {
kasan_violation(addr, size, type, REASON_INVALID_SIZE);
}
vm_size_t rightrz_sz = h->alloc_size - h->left_rz - h->user_size;
/* Check that the redzones are valid */
if (!kasan_check_shadow(addr - h->left_rz, h->left_rz, ASAN_HEAP_LEFT_RZ) ||
!kasan_check_shadow(addr + h->user_size, rightrz_sz, ASAN_HEAP_RIGHT_RZ)) {
kasan_violation(addr, size, type, REASON_BAD_METADATA);
}
/* Check the allocated range is not poisoned */
kasan_check_range((void *)addr, size, type);
}
/*
*
* Quarantine
*
*/
struct freelist_entry {
uint16_t magic;
uint16_t crc;
STAILQ_ENTRY(freelist_entry) list;
union {
struct {
vm_size_t size : 28;
vm_size_t user_size : 28;
vm_size_t frames : BACKTRACE_BITS; /* number of frames in backtrace */
vm_size_t __unused : 8 - BACKTRACE_BITS;
};
uint64_t bits;
};
zone_t zone;
uint32_t backtrace[];
};
_Static_assert(sizeof(struct freelist_entry) <= KASAN_GUARD_PAD, "kasan freelist header exceeds padded size");
struct quarantine {
STAILQ_HEAD(freelist_head, freelist_entry) freelist;
unsigned long entries;
unsigned long max_entries;
vm_size_t size;
vm_size_t max_size;
};
struct quarantine quarantines[] = {
{ STAILQ_HEAD_INITIALIZER((quarantines[KASAN_HEAP_ZALLOC].freelist)), 0, QUARANTINE_ENTRIES, 0, QUARANTINE_MAXSIZE },
{ STAILQ_HEAD_INITIALIZER((quarantines[KASAN_HEAP_KALLOC].freelist)), 0, QUARANTINE_ENTRIES, 0, QUARANTINE_MAXSIZE },
{ STAILQ_HEAD_INITIALIZER((quarantines[KASAN_HEAP_FAKESTACK].freelist)), 0, QUARANTINE_ENTRIES, 0, QUARANTINE_MAXSIZE }
};
static uint16_t
fle_crc(struct freelist_entry *fle)
{
return __nosan_crc16(0, &fle->bits, fle->size - offsetof(struct freelist_entry, bits));
}
/*
* addr, sizep: pointer/size of full allocation including redzone
*/
void NOINLINE
kasan_free_internal(void **addrp, vm_size_t *sizep, int type,
zone_t *zone, vm_size_t user_size, int locked,
bool doquarantine)
{
vm_size_t size = *sizep;
vm_offset_t addr = *(vm_offset_t *)addrp;
assert(type >= 0 && type < KASAN_HEAP_TYPES);
if (type == KASAN_HEAP_KALLOC) {
/* zero-size kalloc allocations are allowed */
assert(!zone);
} else if (type == KASAN_HEAP_ZALLOC) {
assert(zone && user_size);
} else if (type == KASAN_HEAP_FAKESTACK) {
assert(zone && user_size);
}
/* clobber the entire freed region */
kasan_rz_clobber(addr, 0, size, 0);
if (!doquarantine || !quarantine_enabled) {
goto free_current;
}
/* poison the entire freed region */
uint8_t flags = (type == KASAN_HEAP_FAKESTACK) ? ASAN_STACK_FREED : ASAN_HEAP_FREED;
kasan_poison(addr, 0, size, 0, flags);
struct freelist_entry *fle, *tofree = NULL;
struct quarantine *q = &quarantines[type];
assert(size >= sizeof(struct freelist_entry));
/* create a new freelist entry */
fle = (struct freelist_entry *)addr;
fle->magic = magic_for_addr((vm_offset_t)fle, FREE_XOR);
fle->size = size;
fle->user_size = user_size;
fle->frames = 0;
fle->zone = ZONE_NULL;
if (zone) {
fle->zone = *zone;
}
if (type != KASAN_HEAP_FAKESTACK) {
/* don't do expensive things on the fakestack path */
fle->frames = kasan_alloc_bt(fle->backtrace, fle->size - sizeof(struct freelist_entry), 3);
fle->crc = fle_crc(fle);
}
boolean_t flg;
if (!locked) {
kasan_lock(&flg);
}
if (q->size + size > q->max_size) {
/*
* Adding this entry would put us over the max quarantine size. Free the
* larger of the current object and the quarantine head object.
*/
tofree = STAILQ_FIRST(&q->freelist);
if (fle->size > tofree->size) {
goto free_current_locked;
}
}
STAILQ_INSERT_TAIL(&q->freelist, fle, list);
q->entries++;
q->size += size;
/* free the oldest entry, if necessary */
if (tofree || q->entries > q->max_entries) {
tofree = STAILQ_FIRST(&q->freelist);
STAILQ_REMOVE_HEAD(&q->freelist, list);
assert(q->entries > 0 && q->size >= tofree->size);
q->entries--;
q->size -= tofree->size;
if (type != KASAN_HEAP_KALLOC) {
assert((vm_offset_t)zone >= VM_MIN_KERNEL_AND_KEXT_ADDRESS &&
(vm_offset_t)zone <= VM_MAX_KERNEL_ADDRESS);
*zone = tofree->zone;
}
size = tofree->size;
addr = (vm_offset_t)tofree;
/* check the magic and crc match */
if (tofree->magic != magic_for_addr(addr, FREE_XOR)) {
kasan_violation(addr, size, TYPE_UAF, REASON_MOD_AFTER_FREE);
}
if (type != KASAN_HEAP_FAKESTACK && tofree->crc != fle_crc(tofree)) {
kasan_violation(addr, size, TYPE_UAF, REASON_MOD_AFTER_FREE);
}
/* clobber the quarantine header */
__nosan_bzero((void *)addr, sizeof(struct freelist_entry));
} else {
/* quarantine is not full - don't really free anything */
addr = 0;
}
free_current_locked:
if (!locked) {
kasan_unlock(flg);
}
free_current:
*addrp = (void *)addr;
if (addr) {
kasan_unpoison((void *)addr, size);
*sizep = size;
}
}
void NOINLINE
kasan_free(void **addrp, vm_size_t *sizep, int type, zone_t *zone,
vm_size_t user_size, bool quarantine)
{
kasan_free_internal(addrp, sizep, type, zone, user_size, 0, quarantine);
if (free_yield) {
thread_yield_internal(free_yield);
}
}
uptr
__asan_load_cxx_array_cookie(uptr *p)
{
uint8_t *shadow = SHADOW_FOR_ADDRESS((uptr)p);
if (*shadow == ASAN_ARRAY_COOKIE) {
return *p;
} else if (*shadow == ASAN_HEAP_FREED) {
return 0;
} else {
return *p;
}
}
void
__asan_poison_cxx_array_cookie(uptr p)
{
uint8_t *shadow = SHADOW_FOR_ADDRESS(p);
*shadow = ASAN_ARRAY_COOKIE;
}
#define ACCESS_CHECK_DECLARE(type, sz, access) \
void __asan_##type##sz(uptr addr) { \
kasan_check_range((const void *)addr, sz, access); \
} \
void UNSUPPORTED_API(__asan_exp_##type##sz, uptr a, int32_t b);
ACCESS_CHECK_DECLARE(load, 1, TYPE_LOAD);
ACCESS_CHECK_DECLARE(load, 2, TYPE_LOAD);
ACCESS_CHECK_DECLARE(load, 4, TYPE_LOAD);
ACCESS_CHECK_DECLARE(load, 8, TYPE_LOAD);
ACCESS_CHECK_DECLARE(load, 16, TYPE_LOAD);
ACCESS_CHECK_DECLARE(store, 1, TYPE_STORE);
ACCESS_CHECK_DECLARE(store, 2, TYPE_STORE);
ACCESS_CHECK_DECLARE(store, 4, TYPE_STORE);
ACCESS_CHECK_DECLARE(store, 8, TYPE_STORE);
ACCESS_CHECK_DECLARE(store, 16, TYPE_STORE);
void
__asan_loadN(uptr addr, size_t sz)
{
kasan_check_range((const void *)addr, sz, TYPE_LOAD);
}
void
__asan_storeN(uptr addr, size_t sz)
{
kasan_check_range((const void *)addr, sz, TYPE_STORE);
}
static void
kasan_set_shadow(uptr addr, size_t sz, uint8_t val)
{
__nosan_memset((void *)addr, val, sz);
}
#define SET_SHADOW_DECLARE(val) \
void __asan_set_shadow_##val(uptr addr, size_t sz) { \
kasan_set_shadow(addr, sz, 0x##val); \
}
SET_SHADOW_DECLARE(00)
SET_SHADOW_DECLARE(f1)
SET_SHADOW_DECLARE(f2)
SET_SHADOW_DECLARE(f3)
SET_SHADOW_DECLARE(f5)
SET_SHADOW_DECLARE(f8)
/*
* Call 'cb' for each contiguous range of the shadow map. This could be more
* efficient by walking the page table directly.
*/
int
kasan_traverse_mappings(pmap_traverse_callback cb, void *ctx)
{
uintptr_t shadow_base = (uintptr_t)SHADOW_FOR_ADDRESS(VM_MIN_KERNEL_AND_KEXT_ADDRESS);
uintptr_t shadow_top = (uintptr_t)SHADOW_FOR_ADDRESS(VM_MAX_KERNEL_ADDRESS);
shadow_base = vm_map_trunc_page(shadow_base, HW_PAGE_MASK);
shadow_top = vm_map_round_page(shadow_top, HW_PAGE_MASK);
uintptr_t start = 0, end = 0;
for (uintptr_t addr = shadow_base; addr < shadow_top; addr += HW_PAGE_SIZE) {
if (kasan_is_shadow_mapped(addr)) {
if (start == 0) {
start = addr;
}
end = addr + HW_PAGE_SIZE;
} else if (start && end) {
cb(start, end, ctx);
start = end = 0;
}
}
if (start && end) {
cb(start, end, ctx);
}
return 0;
}
/*
* XXX: implement these
*/
UNUSED_ABI(__asan_alloca_poison, uptr addr, uptr size);
UNUSED_ABI(__asan_allocas_unpoison, uptr top, uptr bottom);
UNUSED_ABI(__sanitizer_ptr_sub, uptr a, uptr b);
UNUSED_ABI(__sanitizer_ptr_cmp, uptr a, uptr b);
UNUSED_ABI(__sanitizer_annotate_contiguous_container, const void *a, const void *b, const void *c, const void *d);
UNUSED_ABI(__asan_poison_stack_memory, uptr addr, size_t size);
UNUSED_ABI(__asan_unpoison_stack_memory, uptr a, uptr b);
/*
* Miscellaneous unimplemented asan ABI
*/
UNUSED_ABI(__asan_init, void);
UNUSED_ABI(__asan_register_image_globals, uptr a);
UNUSED_ABI(__asan_unregister_image_globals, uptr a);
UNUSED_ABI(__asan_before_dynamic_init, uptr a);
UNUSED_ABI(__asan_after_dynamic_init, void);
UNUSED_ABI(__asan_version_mismatch_check_v8, void);
UNUSED_ABI(__asan_version_mismatch_check_apple_802, void);
UNUSED_ABI(__asan_version_mismatch_check_apple_900, void);
UNUSED_ABI(__asan_version_mismatch_check_apple_902, void);
UNUSED_ABI(__asan_version_mismatch_check_apple_1000, void);
void UNSUPPORTED_API(__asan_init_v5, void);
void UNSUPPORTED_API(__asan_register_globals, uptr a, uptr b);
void UNSUPPORTED_API(__asan_unregister_globals, uptr a, uptr b);
void UNSUPPORTED_API(__asan_register_elf_globals, uptr a, uptr b, uptr c);
void UNSUPPORTED_API(__asan_unregister_elf_globals, uptr a, uptr b, uptr c);
void UNSUPPORTED_API(__asan_exp_loadN, uptr addr, size_t sz, int32_t e);
void UNSUPPORTED_API(__asan_exp_storeN, uptr addr, size_t sz, int32_t e);
void UNSUPPORTED_API(__asan_report_exp_load_n, uptr addr, unsigned long b, int32_t c);
void UNSUPPORTED_API(__asan_report_exp_store_n, uptr addr, unsigned long b, int32_t c);
/*
*
* SYSCTL
*
*/
static int
sysctl_kasan_test(__unused struct sysctl_oid *oidp, __unused void *arg1, int arg2, struct sysctl_req *req)
{
int mask = 0;
int ch;
int err;
err = sysctl_io_number(req, 0, sizeof(int), &mask, &ch);
if (!err && mask) {
kasan_test(mask, arg2);
}
return err;
}
static int
sysctl_fakestack_enable(__unused struct sysctl_oid *oidp, __unused void *arg1, int __unused arg2, struct sysctl_req *req)
{
int ch, err, val;
err = sysctl_io_number(req, fakestack_enabled, sizeof(fakestack_enabled), &val, &ch);
if (err == 0 && ch) {
fakestack_enabled = !!val;
__asan_option_detect_stack_use_after_return = !!val;
}
return err;
}
SYSCTL_DECL(kasan);
SYSCTL_NODE(_kern, OID_AUTO, kasan, CTLFLAG_RW | CTLFLAG_LOCKED, 0, "");
SYSCTL_COMPAT_INT(_kern_kasan, OID_AUTO, available, CTLFLAG_RD, NULL, KASAN, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, enabled, CTLFLAG_RD, &kasan_enabled, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, checks, CTLFLAG_RW, &enabled_checks, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, quarantine, CTLFLAG_RW, &quarantine_enabled, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, report_ignored, CTLFLAG_RW, &report_ignored, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, free_yield_ms, CTLFLAG_RW, &free_yield, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, memused, CTLFLAG_RD, &shadow_pages_used, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, memtotal, CTLFLAG_RD, &shadow_pages_total, 0, "");
SYSCTL_UINT(_kern_kasan, OID_AUTO, kexts, CTLFLAG_RD, &kexts_loaded, 0, "");
SYSCTL_COMPAT_UINT(_kern_kasan, OID_AUTO, debug, CTLFLAG_RD, NULL, KASAN_DEBUG, "");
SYSCTL_COMPAT_UINT(_kern_kasan, OID_AUTO, zalloc, CTLFLAG_RD, NULL, KASAN_ZALLOC, "");
SYSCTL_COMPAT_UINT(_kern_kasan, OID_AUTO, kalloc, CTLFLAG_RD, NULL, KASAN_KALLOC, "");
SYSCTL_COMPAT_UINT(_kern_kasan, OID_AUTO, dynamicbl, CTLFLAG_RD, NULL, KASAN_DYNAMIC_BLACKLIST, "");
SYSCTL_PROC(_kern_kasan, OID_AUTO, fakestack,
CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
0, 0, sysctl_fakestack_enable, "I", "");
SYSCTL_PROC(_kern_kasan, OID_AUTO, test,
CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
0, 0, sysctl_kasan_test, "I", "");
SYSCTL_PROC(_kern_kasan, OID_AUTO, fail,
CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
0, 1, sysctl_kasan_test, "I", "");
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