//===-- asan_poisoning.cc -------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of AddressSanitizer, an address sanity checker.
//
// Shadow memory poisoning by ASan RTL and by user application.
//===----------------------------------------------------------------------===//
#include "asan_poisoning.h"
#include "asan_report.h"
#include "asan_stack.h"
#include "sanitizer_common/sanitizer_atomic.h"
#include "sanitizer_common/sanitizer_libc.h"
#include "sanitizer_common/sanitizer_flags.h"
namespace __asan {
static atomic_uint8_t can_poison_memory;
void SetCanPoisonMemory(bool value) {
atomic_store(&can_poison_memory, value, memory_order_release);
}
bool CanPoisonMemory() {
return atomic_load(&can_poison_memory, memory_order_acquire);
}
void PoisonShadow(uptr addr, uptr size, u8 value) {
if (!CanPoisonMemory()) return;
CHECK(AddrIsAlignedByGranularity(addr));
CHECK(AddrIsInMem(addr));
CHECK(AddrIsAlignedByGranularity(addr + size));
CHECK(AddrIsInMem(addr + size - SHADOW_GRANULARITY));
CHECK(REAL(memset));
FastPoisonShadow(addr, size, value);
}
void PoisonShadowPartialRightRedzone(uptr addr,
uptr size,
uptr redzone_size,
u8 value) {
if (!CanPoisonMemory()) return;
CHECK(AddrIsAlignedByGranularity(addr));
CHECK(AddrIsInMem(addr));
FastPoisonShadowPartialRightRedzone(addr, size, redzone_size, value);
}
struct ShadowSegmentEndpoint {
u8 *chunk;
s8 offset; // in [0, SHADOW_GRANULARITY)
s8 value; // = *chunk;
explicit ShadowSegmentEndpoint(uptr address) {
chunk = (u8*)MemToShadow(address);
offset = address & (SHADOW_GRANULARITY - 1);
value = *chunk;
}
};
void FlushUnneededASanShadowMemory(uptr p, uptr size) {
// Since asan's mapping is compacting, the shadow chunk may be
// not page-aligned, so we only flush the page-aligned portion.
uptr page_size = GetPageSizeCached();
uptr shadow_beg = RoundUpTo(MemToShadow(p), page_size);
uptr shadow_end = RoundDownTo(MemToShadow(p + size), page_size);
FlushUnneededShadowMemory(shadow_beg, shadow_end - shadow_beg);
}
void AsanPoisonOrUnpoisonIntraObjectRedzone(uptr ptr, uptr size, bool poison) {
uptr end = ptr + size;
if (Verbosity()) {
Printf("__asan_%spoison_intra_object_redzone [%p,%p) %zd\n",
poison ? "" : "un", ptr, end, size);
if (Verbosity() >= 2)
PRINT_CURRENT_STACK();
}
CHECK(size);
CHECK_LE(size, 4096);
CHECK(IsAligned(end, SHADOW_GRANULARITY));
if (!IsAligned(ptr, SHADOW_GRANULARITY)) {
*(u8 *)MemToShadow(ptr) =
poison ? static_cast<u8>(ptr % SHADOW_GRANULARITY) : 0;
ptr |= SHADOW_GRANULARITY - 1;
ptr++;
}
for (; ptr < end; ptr += SHADOW_GRANULARITY)
*(u8*)MemToShadow(ptr) = poison ? kAsanIntraObjectRedzone : 0;
}
} // namespace __asan
// ---------------------- Interface ---------------- {{{1
using namespace __asan; // NOLINT
// Current implementation of __asan_(un)poison_memory_region doesn't check
// that user program (un)poisons the memory it owns. It poisons memory
// conservatively, and unpoisons progressively to make sure asan shadow
// mapping invariant is preserved (see detailed mapping description here:
// https://github.com/google/sanitizers/wiki/AddressSanitizerAlgorithm).
//
// * if user asks to poison region [left, right), the program poisons
// at least [left, AlignDown(right)).
// * if user asks to unpoison region [left, right), the program unpoisons
// at most [AlignDown(left), right).
void __asan_poison_memory_region(void const volatile *addr, uptr size) {
if (!flags()->allow_user_poisoning || size == 0) return;
uptr beg_addr = (uptr)addr;
uptr end_addr = beg_addr + size;
VPrintf(3, "Trying to poison memory region [%p, %p)\n", (void *)beg_addr,
(void *)end_addr);
ShadowSegmentEndpoint beg(beg_addr);
ShadowSegmentEndpoint end(end_addr);
if (beg.chunk == end.chunk) {
CHECK(beg.offset < end.offset);
s8 value = beg.value;
CHECK(value == end.value);
// We can only poison memory if the byte in end.offset is unaddressable.
// No need to re-poison memory if it is poisoned already.
if (value > 0 && value <= end.offset) {
if (beg.offset > 0) {
*beg.chunk = Min(value, beg.offset);
} else {
*beg.chunk = kAsanUserPoisonedMemoryMagic;
}
}
return;
}
CHECK(beg.chunk < end.chunk);
if (beg.offset > 0) {
// Mark bytes from beg.offset as unaddressable.
if (beg.value == 0) {
*beg.chunk = beg.offset;
} else {
*beg.chunk = Min(beg.value, beg.offset);
}
beg.chunk++;
}
REAL(memset)(beg.chunk, kAsanUserPoisonedMemoryMagic, end.chunk - beg.chunk);
// Poison if byte in end.offset is unaddressable.
if (end.value > 0 && end.value <= end.offset) {
*end.chunk = kAsanUserPoisonedMemoryMagic;
}
}
void __asan_unpoison_memory_region(void const volatile *addr, uptr size) {
if (!flags()->allow_user_poisoning || size == 0) return;
uptr beg_addr = (uptr)addr;
uptr end_addr = beg_addr + size;
VPrintf(3, "Trying to unpoison memory region [%p, %p)\n", (void *)beg_addr,
(void *)end_addr);
ShadowSegmentEndpoint beg(beg_addr);
ShadowSegmentEndpoint end(end_addr);
if (beg.chunk == end.chunk) {
CHECK(beg.offset < end.offset);
s8 value = beg.value;
CHECK(value == end.value);
// We unpoison memory bytes up to enbytes up to end.offset if it is not
// unpoisoned already.
if (value != 0) {
*beg.chunk = Max(value, end.offset);
}
return;
}
CHECK(beg.chunk < end.chunk);
if (beg.offset > 0) {
*beg.chunk = 0;
beg.chunk++;
}
REAL(memset)(beg.chunk, 0, end.chunk - beg.chunk);
if (end.offset > 0 && end.value != 0) {
*end.chunk = Max(end.value, end.offset);
}
}
int __asan_address_is_poisoned(void const volatile *addr) {
return __asan::AddressIsPoisoned((uptr)addr);
}
uptr __asan_region_is_poisoned(uptr beg, uptr size) {
if (!size) return 0;
uptr end = beg + size;
if (!AddrIsInMem(beg)) return beg;
if (!AddrIsInMem(end)) return end;
CHECK_LT(beg, end);
uptr aligned_b = RoundUpTo(beg, SHADOW_GRANULARITY);
uptr aligned_e = RoundDownTo(end, SHADOW_GRANULARITY);
uptr shadow_beg = MemToShadow(aligned_b);
uptr shadow_end = MemToShadow(aligned_e);
// First check the first and the last application bytes,
// then check the SHADOW_GRANULARITY-aligned region by calling
// mem_is_zero on the corresponding shadow.
if (!__asan::AddressIsPoisoned(beg) &&
!__asan::AddressIsPoisoned(end - 1) &&
(shadow_end <= shadow_beg ||
__sanitizer::mem_is_zero((const char *)shadow_beg,
shadow_end - shadow_beg)))
return 0;
// The fast check failed, so we have a poisoned byte somewhere.
// Find it slowly.
for (; beg < end; beg++)
if (__asan::AddressIsPoisoned(beg))
return beg;
UNREACHABLE("mem_is_zero returned false, but poisoned byte was not found");
return 0;
}
#define CHECK_SMALL_REGION(p, size, isWrite) \
do { \
uptr __p = reinterpret_cast<uptr>(p); \
uptr __size = size; \
if (UNLIKELY(__asan::AddressIsPoisoned(__p) || \
__asan::AddressIsPoisoned(__p + __size - 1))) { \
GET_CURRENT_PC_BP_SP; \
uptr __bad = __asan_region_is_poisoned(__p, __size); \
__asan_report_error(pc, bp, sp, __bad, isWrite, __size, 0);\
} \
} while (false); \
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
u16 __sanitizer_unaligned_load16(const uu16 *p) {
CHECK_SMALL_REGION(p, sizeof(*p), false);
return *p;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
u32 __sanitizer_unaligned_load32(const uu32 *p) {
CHECK_SMALL_REGION(p, sizeof(*p), false);
return *p;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
u64 __sanitizer_unaligned_load64(const uu64 *p) {
CHECK_SMALL_REGION(p, sizeof(*p), false);
return *p;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
void __sanitizer_unaligned_store16(uu16 *p, u16 x) {
CHECK_SMALL_REGION(p, sizeof(*p), true);
*p = x;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
void __sanitizer_unaligned_store32(uu32 *p, u32 x) {
CHECK_SMALL_REGION(p, sizeof(*p), true);
*p = x;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
void __sanitizer_unaligned_store64(uu64 *p, u64 x) {
CHECK_SMALL_REGION(p, sizeof(*p), true);
*p = x;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
void __asan_poison_cxx_array_cookie(uptr p) {
if (SANITIZER_WORDSIZE != 64) return;
if (!flags()->poison_array_cookie) return;
uptr s = MEM_TO_SHADOW(p);
*reinterpret_cast<u8*>(s) = kAsanArrayCookieMagic;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
uptr __asan_load_cxx_array_cookie(uptr *p) {
if (SANITIZER_WORDSIZE != 64) return *p;
if (!flags()->poison_array_cookie) return *p;
uptr s = MEM_TO_SHADOW(reinterpret_cast<uptr>(p));
u8 sval = *reinterpret_cast<u8*>(s);
if (sval == kAsanArrayCookieMagic) return *p;
// If sval is not kAsanArrayCookieMagic it can only be freed memory,
// which means that we are going to get double-free. So, return 0 to avoid
// infinite loop of destructors. We don't want to report a double-free here
// though, so print a warning just in case.
// CHECK_EQ(sval, kAsanHeapFreeMagic);
if (sval == kAsanHeapFreeMagic) {
Report("AddressSanitizer: loaded array cookie from free-d memory; "
"expect a double-free report\n");
return 0;
}
// The cookie may remain unpoisoned if e.g. it comes from a custom
// operator new defined inside a class.
return *p;
}
// This is a simplified version of __asan_(un)poison_memory_region, which
// assumes that left border of region to be poisoned is properly aligned.
static void PoisonAlignedStackMemory(uptr addr, uptr size, bool do_poison) {
if (size == 0) return;
uptr aligned_size = size & ~(SHADOW_GRANULARITY - 1);
PoisonShadow(addr, aligned_size,
do_poison ? kAsanStackUseAfterScopeMagic : 0);
if (size == aligned_size)
return;
s8 end_offset = (s8)(size - aligned_size);
s8* shadow_end = (s8*)MemToShadow(addr + aligned_size);
s8 end_value = *shadow_end;
if (do_poison) {
// If possible, mark all the bytes mapping to last shadow byte as
// unaddressable.
if (end_value > 0 && end_value <= end_offset)
*shadow_end = (s8)kAsanStackUseAfterScopeMagic;
} else {
// If necessary, mark few first bytes mapping to last shadow byte
// as addressable
if (end_value != 0)
*shadow_end = Max(end_value, end_offset);
}
}
void __asan_poison_stack_memory(uptr addr, uptr size) {
VReport(1, "poisoning: %p %zx\n", (void *)addr, size);
PoisonAlignedStackMemory(addr, size, true);
}
void __asan_unpoison_stack_memory(uptr addr, uptr size) {
VReport(1, "unpoisoning: %p %zx\n", (void *)addr, size);
PoisonAlignedStackMemory(addr, size, false);
}
void __sanitizer_annotate_contiguous_container(const void *beg_p,
const void *end_p,
const void *old_mid_p,
const void *new_mid_p) {
if (!flags()->detect_container_overflow) return;
VPrintf(2, "contiguous_container: %p %p %p %p\n", beg_p, end_p, old_mid_p,
new_mid_p);
uptr beg = reinterpret_cast<uptr>(beg_p);
uptr end = reinterpret_cast<uptr>(end_p);
uptr old_mid = reinterpret_cast<uptr>(old_mid_p);
uptr new_mid = reinterpret_cast<uptr>(new_mid_p);
uptr granularity = SHADOW_GRANULARITY;
if (!(beg <= old_mid && beg <= new_mid && old_mid <= end && new_mid <= end &&
IsAligned(beg, granularity))) {
GET_STACK_TRACE_FATAL_HERE;
ReportBadParamsToAnnotateContiguousContainer(beg, end, old_mid, new_mid,
&stack);
}
CHECK_LE(end - beg,
FIRST_32_SECOND_64(1UL << 30, 1UL << 34)); // Sanity check.
uptr a = RoundDownTo(Min(old_mid, new_mid), granularity);
uptr c = RoundUpTo(Max(old_mid, new_mid), granularity);
uptr d1 = RoundDownTo(old_mid, granularity);
// uptr d2 = RoundUpTo(old_mid, granularity);
// Currently we should be in this state:
// [a, d1) is good, [d2, c) is bad, [d1, d2) is partially good.
// Make a quick sanity check that we are indeed in this state.
//
// FIXME: Two of these three checks are disabled until we fix
// https://github.com/google/sanitizers/issues/258.
// if (d1 != d2)
// CHECK_EQ(*(u8*)MemToShadow(d1), old_mid - d1);
if (a + granularity <= d1)
CHECK_EQ(*(u8*)MemToShadow(a), 0);
// if (d2 + granularity <= c && c <= end)
// CHECK_EQ(*(u8 *)MemToShadow(c - granularity),
// kAsanContiguousContainerOOBMagic);
uptr b1 = RoundDownTo(new_mid, granularity);
uptr b2 = RoundUpTo(new_mid, granularity);
// New state:
// [a, b1) is good, [b2, c) is bad, [b1, b2) is partially good.
PoisonShadow(a, b1 - a, 0);
PoisonShadow(b2, c - b2, kAsanContiguousContainerOOBMagic);
if (b1 != b2) {
CHECK_EQ(b2 - b1, granularity);
*(u8*)MemToShadow(b1) = static_cast<u8>(new_mid - b1);
}
}
const void *__sanitizer_contiguous_container_find_bad_address(
const void *beg_p, const void *mid_p, const void *end_p) {
if (!flags()->detect_container_overflow)
return nullptr;
uptr beg = reinterpret_cast<uptr>(beg_p);
uptr end = reinterpret_cast<uptr>(end_p);
uptr mid = reinterpret_cast<uptr>(mid_p);
CHECK_LE(beg, mid);
CHECK_LE(mid, end);
// Check some bytes starting from beg, some bytes around mid, and some bytes
// ending with end.
uptr kMaxRangeToCheck = 32;
uptr r1_beg = beg;
uptr r1_end = Min(end + kMaxRangeToCheck, mid);
uptr r2_beg = Max(beg, mid - kMaxRangeToCheck);
uptr r2_end = Min(end, mid + kMaxRangeToCheck);
uptr r3_beg = Max(end - kMaxRangeToCheck, mid);
uptr r3_end = end;
for (uptr i = r1_beg; i < r1_end; i++)
if (AddressIsPoisoned(i))
return reinterpret_cast<const void *>(i);
for (uptr i = r2_beg; i < mid; i++)
if (AddressIsPoisoned(i))
return reinterpret_cast<const void *>(i);
for (uptr i = mid; i < r2_end; i++)
if (!AddressIsPoisoned(i))
return reinterpret_cast<const void *>(i);
for (uptr i = r3_beg; i < r3_end; i++)
if (!AddressIsPoisoned(i))
return reinterpret_cast<const void *>(i);
return nullptr;
}
int __sanitizer_verify_contiguous_container(const void *beg_p,
const void *mid_p,
const void *end_p) {
return __sanitizer_contiguous_container_find_bad_address(beg_p, mid_p,
end_p) == nullptr;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
void __asan_poison_intra_object_redzone(uptr ptr, uptr size) {
AsanPoisonOrUnpoisonIntraObjectRedzone(ptr, size, true);
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
void __asan_unpoison_intra_object_redzone(uptr ptr, uptr size) {
AsanPoisonOrUnpoisonIntraObjectRedzone(ptr, size, false);
}
// --- Implementation of LSan-specific functions --- {{{1
namespace __lsan {
bool WordIsPoisoned(uptr addr) {
return (__asan_region_is_poisoned(addr, sizeof(uptr)) != 0);
}
}