libsanitizer/asan/asan_poisoning.cc

   1 //===-- asan_poisoning.cc -------------------------------------------------===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // This file is a part of AddressSanitizer, an address sanity checker.
   9 //
  10 // Shadow memory poisoning by ASan RTL and by user application.
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "asan_poisoning.h"
  14 #include "asan_report.h"
  15 #include "asan_stack.h"
  16 #include "sanitizer_common/sanitizer_libc.h"
  17 #include "sanitizer_common/sanitizer_flags.h"
  18
  19 namespace __asan {
  20
  21 void PoisonShadow(uptr addr, uptr size, u8 value) {
  22   if (!flags()->poison_heap) return;
  23   CHECK(AddrIsAlignedByGranularity(addr));
  24   CHECK(AddrIsInMem(addr));
  25   CHECK(AddrIsAlignedByGranularity(addr + size));
  26   CHECK(AddrIsInMem(addr + size - SHADOW_GRANULARITY));
  27   CHECK(REAL(memset));
  28   FastPoisonShadow(addr, size, value);
  29 }
  30
  31 void PoisonShadowPartialRightRedzone(uptr addr,
  32                                      uptr size,
  33                                      uptr redzone_size,
  34                                      u8 value) {
  35   if (!flags()->poison_heap) return;
  36   CHECK(AddrIsAlignedByGranularity(addr));
  37   CHECK(AddrIsInMem(addr));
  38   FastPoisonShadowPartialRightRedzone(addr, size, redzone_size, value);
  39 }
  40
  41 struct ShadowSegmentEndpoint {
  42   u8 *chunk;
  43   s8 offset;  // in [0, SHADOW_GRANULARITY)
  44   s8 value;  // = *chunk;
  45
  46   explicit ShadowSegmentEndpoint(uptr address) {
  47     chunk = (u8*)MemToShadow(address);
  48     offset = address & (SHADOW_GRANULARITY - 1);
  49     value = *chunk;
  50   }
  51 };
  52
  53 void FlushUnneededASanShadowMemory(uptr p, uptr size) {
  54     // Since asan's mapping is compacting, the shadow chunk may be
  55     // not page-aligned, so we only flush the page-aligned portion.
  56     uptr page_size = GetPageSizeCached();
  57     uptr shadow_beg = RoundUpTo(MemToShadow(p), page_size);
  58     uptr shadow_end = RoundDownTo(MemToShadow(p + size), page_size);
  59     FlushUnneededShadowMemory(shadow_beg, shadow_end - shadow_beg);
  60 }
  61
  62 }  // namespace __asan
  63
  64 // ---------------------- Interface ---------------- {{{1
  65 using namespace __asan;  // NOLINT
  66
  67 // Current implementation of __asan_(un)poison_memory_region doesn't check
  68 // that user program (un)poisons the memory it owns. It poisons memory
  69 // conservatively, and unpoisons progressively to make sure asan shadow
  70 // mapping invariant is preserved (see detailed mapping description here:
  71 // http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm).
  72 //
  73 // * if user asks to poison region [left, right), the program poisons
  74 // at least [left, AlignDown(right)).
  75 // * if user asks to unpoison region [left, right), the program unpoisons
  76 // at most [AlignDown(left), right).
  77 void __asan_poison_memory_region(void const volatile *addr, uptr size) {
  78   if (!flags()->allow_user_poisoning || size == 0) return;
  79   uptr beg_addr = (uptr)addr;
  80   uptr end_addr = beg_addr + size;
  81   VPrintf(1, "Trying to poison memory region [%p, %p)\n", (void *)beg_addr,
  82           (void *)end_addr);
  83   ShadowSegmentEndpoint beg(beg_addr);
  84   ShadowSegmentEndpoint end(end_addr);
  85   if (beg.chunk == end.chunk) {
  86     CHECK(beg.offset < end.offset);
  87     s8 value = beg.value;
  88     CHECK(value == end.value);
  89     // We can only poison memory if the byte in end.offset is unaddressable.
  90     // No need to re-poison memory if it is poisoned already.
  91     if (value > 0 && value <= end.offset) {
  92       if (beg.offset > 0) {
  93         *beg.chunk = Min(value, beg.offset);
  94       } else {
  95         *beg.chunk = kAsanUserPoisonedMemoryMagic;
  96       }
  97     }
  98     return;
  99   }
 100   CHECK(beg.chunk < end.chunk);
 101   if (beg.offset > 0) {
 102     // Mark bytes from beg.offset as unaddressable.
 103     if (beg.value == 0) {
 104       *beg.chunk = beg.offset;
 105     } else {
 106       *beg.chunk = Min(beg.value, beg.offset);
 107     }
 108     beg.chunk++;
 109   }
 110   REAL(memset)(beg.chunk, kAsanUserPoisonedMemoryMagic, end.chunk - beg.chunk);
 111   // Poison if byte in end.offset is unaddressable.
 112   if (end.value > 0 && end.value <= end.offset) {
 113     *end.chunk = kAsanUserPoisonedMemoryMagic;
 114   }
 115 }
 116
 117 void __asan_unpoison_memory_region(void const volatile *addr, uptr size) {
 118   if (!flags()->allow_user_poisoning || size == 0) return;
 119   uptr beg_addr = (uptr)addr;
 120   uptr end_addr = beg_addr + size;
 121   VPrintf(1, "Trying to unpoison memory region [%p, %p)\n", (void *)beg_addr,
 122           (void *)end_addr);
 123   ShadowSegmentEndpoint beg(beg_addr);
 124   ShadowSegmentEndpoint end(end_addr);
 125   if (beg.chunk == end.chunk) {
 126     CHECK(beg.offset < end.offset);
 127     s8 value = beg.value;
 128     CHECK(value == end.value);
 129     // We unpoison memory bytes up to enbytes up to end.offset if it is not
 130     // unpoisoned already.
 131     if (value != 0) {
 132       *beg.chunk = Max(value, end.offset);
 133     }
 134     return;
 135   }
 136   CHECK(beg.chunk < end.chunk);
 137   if (beg.offset > 0) {
 138     *beg.chunk = 0;
 139     beg.chunk++;
 140   }
 141   REAL(memset)(beg.chunk, 0, end.chunk - beg.chunk);
 142   if (end.offset > 0 && end.value != 0) {
 143     *end.chunk = Max(end.value, end.offset);
 144   }
 145 }
 146
 147 int __asan_address_is_poisoned(void const volatile *addr) {
 148   return __asan::AddressIsPoisoned((uptr)addr);
 149 }
 150
 151 uptr __asan_region_is_poisoned(uptr beg, uptr size) {
 152   if (!size) return 0;
 153   uptr end = beg + size;
 154   if (!AddrIsInMem(beg)) return beg;
 155   if (!AddrIsInMem(end)) return end;
 156   CHECK_LT(beg, end);
 157   uptr aligned_b = RoundUpTo(beg, SHADOW_GRANULARITY);
 158   uptr aligned_e = RoundDownTo(end, SHADOW_GRANULARITY);
 159   uptr shadow_beg = MemToShadow(aligned_b);
 160   uptr shadow_end = MemToShadow(aligned_e);
 161   // First check the first and the last application bytes,
 162   // then check the SHADOW_GRANULARITY-aligned region by calling
 163   // mem_is_zero on the corresponding shadow.
 164   if (!__asan::AddressIsPoisoned(beg) &&
 165       !__asan::AddressIsPoisoned(end - 1) &&
 166       (shadow_end <= shadow_beg ||
 167        __sanitizer::mem_is_zero((const char *)shadow_beg,
 168                                 shadow_end - shadow_beg)))
 169     return 0;
 170   // The fast check failed, so we have a poisoned byte somewhere.
 171   // Find it slowly.
 172   for (; beg < end; beg++)
 173     if (__asan::AddressIsPoisoned(beg))
 174       return beg;
 175   UNREACHABLE("mem_is_zero returned false, but poisoned byte was not found");
 176   return 0;
 177 }
 178
 179 #define CHECK_SMALL_REGION(p, size, isWrite)                  \
 180   do {                                                        \
 181     uptr __p = reinterpret_cast<uptr>(p);                     \
 182     uptr __size = size;                                       \
 183     if (UNLIKELY(__asan::AddressIsPoisoned(__p) ||            \
 184         __asan::AddressIsPoisoned(__p + __size - 1))) {       \
 185       GET_CURRENT_PC_BP_SP;                                   \
 186       uptr __bad = __asan_region_is_poisoned(__p, __size);    \
 187       __asan_report_error(pc, bp, sp, __bad, isWrite, __size);\
 188     }                                                         \
 189   } while (false);                                            \
 190
 191
 192 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 193 u16 __sanitizer_unaligned_load16(const uu16 *p) {
 194   CHECK_SMALL_REGION(p, sizeof(*p), false);
 195   return *p;
 196 }
 197
 198 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 199 u32 __sanitizer_unaligned_load32(const uu32 *p) {
 200   CHECK_SMALL_REGION(p, sizeof(*p), false);
 201   return *p;
 202 }
 203
 204 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 205 u64 __sanitizer_unaligned_load64(const uu64 *p) {
 206   CHECK_SMALL_REGION(p, sizeof(*p), false);
 207   return *p;
 208 }
 209
 210 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 211 void __sanitizer_unaligned_store16(uu16 *p, u16 x) {
 212   CHECK_SMALL_REGION(p, sizeof(*p), true);
 213   *p = x;
 214 }
 215
 216 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 217 void __sanitizer_unaligned_store32(uu32 *p, u32 x) {
 218   CHECK_SMALL_REGION(p, sizeof(*p), true);
 219   *p = x;
 220 }
 221
 222 extern "C" SANITIZER_INTERFACE_ATTRIBUTE
 223 void __sanitizer_unaligned_store64(uu64 *p, u64 x) {
 224   CHECK_SMALL_REGION(p, sizeof(*p), true);
 225   *p = x;
 226 }
 227
 228 // This is a simplified version of __asan_(un)poison_memory_region, which
 229 // assumes that left border of region to be poisoned is properly aligned.
 230 static void PoisonAlignedStackMemory(uptr addr, uptr size, bool do_poison) {
 231   if (size == 0) return;
 232   uptr aligned_size = size & ~(SHADOW_GRANULARITY - 1);
 233   PoisonShadow(addr, aligned_size,
 234                do_poison ? kAsanStackUseAfterScopeMagic : 0);
 235   if (size == aligned_size)
 236     return;
 237   s8 end_offset = (s8)(size - aligned_size);
 238   s8* shadow_end = (s8*)MemToShadow(addr + aligned_size);
 239   s8 end_value = *shadow_end;
 240   if (do_poison) {
 241     // If possible, mark all the bytes mapping to last shadow byte as
 242     // unaddressable.
 243     if (end_value > 0 && end_value <= end_offset)
 244       *shadow_end = (s8)kAsanStackUseAfterScopeMagic;
 245   } else {
 246     // If necessary, mark few first bytes mapping to last shadow byte
 247     // as addressable
 248     if (end_value != 0)
 249       *shadow_end = Max(end_value, end_offset);
 250   }
 251 }
 252
 253 void __asan_poison_stack_memory(uptr addr, uptr size) {
 254   VReport(1, "poisoning: %p %zx\n", (void *)addr, size);
 255   PoisonAlignedStackMemory(addr, size, true);
 256 }
 257
 258 void __asan_unpoison_stack_memory(uptr addr, uptr size) {
 259   VReport(1, "unpoisoning: %p %zx\n", (void *)addr, size);
 260   PoisonAlignedStackMemory(addr, size, false);
 261 }
 262
 263 void __sanitizer_annotate_contiguous_container(const void *beg_p,
 264                                                const void *end_p,
 265                                                const void *old_mid_p,
 266                                                const void *new_mid_p) {
 267   if (!flags()->detect_container_overflow) return;
 268   VPrintf(2, "contiguous_container: %p %p %p %p\n", beg_p, end_p, old_mid_p,
 269           new_mid_p);
 270   uptr beg = reinterpret_cast<uptr>(beg_p);
 271   uptr end = reinterpret_cast<uptr>(end_p);
 272   uptr old_mid = reinterpret_cast<uptr>(old_mid_p);
 273   uptr new_mid = reinterpret_cast<uptr>(new_mid_p);
 274   uptr granularity = SHADOW_GRANULARITY;
 275   if (!(beg <= old_mid && beg <= new_mid && old_mid <= end && new_mid <= end &&
 276         IsAligned(beg, granularity))) {
 277     GET_STACK_TRACE_FATAL_HERE;
 278     ReportBadParamsToAnnotateContiguousContainer(beg, end, old_mid, new_mid,
 279                                                  &stack);
 280   }
 281   CHECK_LE(end - beg,
 282            FIRST_32_SECOND_64(1UL << 30, 1UL << 34)); // Sanity check.
 283
 284   uptr a = RoundDownTo(Min(old_mid, new_mid), granularity);
 285   uptr c = RoundUpTo(Max(old_mid, new_mid), granularity);
 286   uptr d1 = RoundDownTo(old_mid, granularity);
 287   // uptr d2 = RoundUpTo(old_mid, granularity);
 288   // Currently we should be in this state:
 289   // [a, d1) is good, [d2, c) is bad, [d1, d2) is partially good.
 290   // Make a quick sanity check that we are indeed in this state.
 291   //
 292   // FIXME: Two of these three checks are disabled until we fix
 293   // https://code.google.com/p/address-sanitizer/issues/detail?id=258.
 294   // if (d1 != d2)
 295   //  CHECK_EQ(*(u8*)MemToShadow(d1), old_mid - d1);
 296   if (a + granularity <= d1)
 297     CHECK_EQ(*(u8*)MemToShadow(a), 0);
 298   // if (d2 + granularity <= c && c <= end)
 299   //   CHECK_EQ(*(u8 *)MemToShadow(c - granularity),
 300   //            kAsanContiguousContainerOOBMagic);
 301
 302   uptr b1 = RoundDownTo(new_mid, granularity);
 303   uptr b2 = RoundUpTo(new_mid, granularity);
 304   // New state:
 305   // [a, b1) is good, [b2, c) is bad, [b1, b2) is partially good.
 306   PoisonShadow(a, b1 - a, 0);
 307   PoisonShadow(b2, c - b2, kAsanContiguousContainerOOBMagic);
 308   if (b1 != b2) {
 309     CHECK_EQ(b2 - b1, granularity);
 310     *(u8*)MemToShadow(b1) = static_cast<u8>(new_mid - b1);
 311   }
 312 }
 313
 314 int __sanitizer_verify_contiguous_container(const void *beg_p,
 315                                             const void *mid_p,
 316                                             const void *end_p) {
 317   if (!flags()->detect_container_overflow) return 1;
 318   uptr beg = reinterpret_cast<uptr>(beg_p);
 319   uptr end = reinterpret_cast<uptr>(end_p);
 320   uptr mid = reinterpret_cast<uptr>(mid_p);
 321   CHECK_LE(beg, mid);
 322   CHECK_LE(mid, end);
 323   // Check some bytes starting from beg, some bytes around mid, and some bytes
 324   // ending with end.
 325   uptr kMaxRangeToCheck = 32;
 326   uptr r1_beg = beg;
 327   uptr r1_end = Min(end + kMaxRangeToCheck, mid);
 328   uptr r2_beg = Max(beg, mid - kMaxRangeToCheck);
 329   uptr r2_end = Min(end, mid + kMaxRangeToCheck);
 330   uptr r3_beg = Max(end - kMaxRangeToCheck, mid);
 331   uptr r3_end = end;
 332   for (uptr i = r1_beg; i < r1_end; i++)
 333     if (AddressIsPoisoned(i))
 334       return 0;
 335   for (uptr i = r2_beg; i < mid; i++)
 336     if (AddressIsPoisoned(i))
 337       return 0;
 338   for (uptr i = mid; i < r2_end; i++)
 339     if (!AddressIsPoisoned(i))
 340       return 0;
 341   for (uptr i = r3_beg; i < r3_end; i++)
 342     if (!AddressIsPoisoned(i))
 343       return 0;
 344   return 1;
 345 }
 346 // --- Implementation of LSan-specific functions --- {{{1
 347 namespace __lsan {
 348 bool WordIsPoisoned(uptr addr) {
 349   return (__asan_region_is_poisoned(addr, sizeof(uptr)) != 0);
 350 }
 351 }