asan_report.cc   [plain text]

//===-- asan_report.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.
//
// This file contains error reporting code.
//===----------------------------------------------------------------------===//
#include "asan_flags.h"
#include "asan_internal.h"
#include "asan_mapping.h"
#include "asan_report.h"
#include "asan_stack.h"
#include "asan_thread.h"
#include "asan_thread_registry.h"

namespace __asan {

// -------------------- User-specified callbacks ----------------- {{{1
static void (*error_report_callback)(const char*);
static char *error_message_buffer = 0;
static uptr error_message_buffer_pos = 0;
static uptr error_message_buffer_size = 0;

void AppendToErrorMessageBuffer(const char *buffer) {
  if (error_message_buffer) {
    uptr length = internal_strlen(buffer);
    CHECK_GE(error_message_buffer_size, error_message_buffer_pos);
    uptr remaining = error_message_buffer_size - error_message_buffer_pos;
    internal_strncpy(error_message_buffer + error_message_buffer_pos,
                     buffer, remaining);
    error_message_buffer[error_message_buffer_size - 1] = '\0';
    // FIXME: reallocate the buffer instead of truncating the message.
    error_message_buffer_pos += remaining > length ? length : remaining;
  }
}

// ---------------------- Helper functions ----------------------- {{{1

static void PrintBytes(const char *before, uptr *a) {
  u8 *bytes = (u8*)a;
  uptr byte_num = (__WORDSIZE) / 8;
  Printf("%s%p:", before, (void*)a);
  for (uptr i = 0; i < byte_num; i++) {
    Printf(" %x%x", bytes[i] >> 4, bytes[i] & 15);
  }
  Printf("\n");
}

static void PrintShadowMemoryForAddress(uptr addr) {
  if (!AddrIsInMem(addr))
    return;
  uptr shadow_addr = MemToShadow(addr);
  Printf("Shadow byte and word:\n");
  Printf("  %p: %x\n", (void*)shadow_addr, *(unsigned char*)shadow_addr);
  uptr aligned_shadow = shadow_addr & ~(kWordSize - 1);
  PrintBytes("  ", (uptr*)(aligned_shadow));
  Printf("More shadow bytes:\n");
  for (int i = -4; i <= 4; i++) {
    const char *prefix = (i == 0) ? "=>" : "  ";
    PrintBytes(prefix, (uptr*)(aligned_shadow + i * kWordSize));
  }
}

static void PrintZoneForPointer(uptr ptr, uptr zone_ptr,
                                const char *zone_name) {
  if (zone_ptr) {
    if (zone_name) {
      Printf("malloc_zone_from_ptr(%p) = %p, which is %s\n",
                 ptr, zone_ptr, zone_name);
    } else {
      Printf("malloc_zone_from_ptr(%p) = %p, which doesn't have a name\n",
                 ptr, zone_ptr);
    }
  } else {
    Printf("malloc_zone_from_ptr(%p) = 0\n", ptr);
  }
}

// ---------------------- Address Descriptions ------------------- {{{1

static bool IsASCII(unsigned char c) {
  return /*0x00 <= c &&*/ c <= 0x7F;
}

// Check if the global is a zero-terminated ASCII string. If so, print it.
static void PrintGlobalNameIfASCII(const __asan_global &g) {
  for (uptr p = g.beg; p < g.beg + g.size - 1; p++) {
    if (!IsASCII(*(unsigned char*)p)) return;
  }
  if (*(char*)(g.beg + g.size - 1) != 0) return;
  Printf("  '%s' is ascii string '%s'\n", g.name, (char*)g.beg);
}

bool DescribeAddressRelativeToGlobal(uptr addr, const __asan_global &g) {
  if (addr < g.beg - kGlobalAndStackRedzone) return false;
  if (addr >= g.beg + g.size_with_redzone) return false;
  Printf("%p is located ", (void*)addr);
  if (addr < g.beg) {
    Printf("%zd bytes to the left", g.beg - addr);
  } else if (addr >= g.beg + g.size) {
    Printf("%zd bytes to the right", addr - (g.beg + g.size));
  } else {
    Printf("%zd bytes inside", addr - g.beg);  // Can it happen?
  }
  Printf(" of global variable '%s' (0x%zx) of size %zu\n",
             g.name, g.beg, g.size);
  PrintGlobalNameIfASCII(g);
  return true;
}

bool DescribeAddressIfShadow(uptr addr) {
  if (AddrIsInMem(addr))
    return false;
  static const char kAddrInShadowReport[] =
      "Address %p is located in the %s.\n";
  if (AddrIsInShadowGap(addr)) {
    Printf(kAddrInShadowReport, addr, "shadow gap area");
    return true;
  }
  if (AddrIsInHighShadow(addr)) {
    Printf(kAddrInShadowReport, addr, "high shadow area");
    return true;
  }
  if (AddrIsInLowShadow(addr)) {
    Printf(kAddrInShadowReport, addr, "low shadow area");
    return true;
  }
  CHECK(0 && "Address is not in memory and not in shadow?");
  return false;
}

bool DescribeAddressIfStack(uptr addr, uptr access_size) {
  AsanThread *t = asanThreadRegistry().FindThreadByStackAddress(addr);
  if (!t) return false;
  const sptr kBufSize = 4095;
  char buf[kBufSize];
  uptr offset = 0;
  const char *frame_descr = t->GetFrameNameByAddr(addr, &offset);
  // This string is created by the compiler and has the following form:
  // "FunctioName n alloc_1 alloc_2 ... alloc_n"
  // where alloc_i looks like "offset size len ObjectName ".
  CHECK(frame_descr);
  // Report the function name and the offset.
  const char *name_end = internal_strchr(frame_descr, ' ');
  CHECK(name_end);
  buf[0] = 0;
  internal_strncat(buf, frame_descr,
                   Min(kBufSize,
                       static_cast<sptr>(name_end - frame_descr)));
  Printf("Address %p is located at offset %zu "
             "in frame <%s> of T%d's stack:\n",
             (void*)addr, offset, buf, t->tid());
  // Report the number of stack objects.
  char *p;
  uptr n_objects = internal_simple_strtoll(name_end, &p, 10);
  CHECK(n_objects > 0);
  Printf("  This frame has %zu object(s):\n", n_objects);
  // Report all objects in this frame.
  for (uptr i = 0; i < n_objects; i++) {
    uptr beg, size;
    sptr len;
    beg  = internal_simple_strtoll(p, &p, 10);
    size = internal_simple_strtoll(p, &p, 10);
    len  = internal_simple_strtoll(p, &p, 10);
    if (beg <= 0 || size <= 0 || len < 0 || *p != ' ') {
      Printf("AddressSanitizer can't parse the stack frame "
                 "descriptor: |%s|\n", frame_descr);
      break;
    }
    p++;
    buf[0] = 0;
    internal_strncat(buf, p, Min(kBufSize, len));
    p += len;
    Printf("    [%zu, %zu) '%s'\n", beg, beg + size, buf);
  }
  Printf("HINT: this may be a false positive if your program uses "
             "some custom stack unwind mechanism\n"
             "      (longjmp and C++ exceptions *are* supported)\n");
  DescribeThread(t->summary());
  return true;
}

static void DescribeAccessToHeapChunk(AsanChunkView chunk, uptr addr,
                                      uptr access_size) {
  uptr offset;
  Printf("%p is located ", (void*)addr);
  if (chunk.AddrIsInside(addr, access_size, &offset)) {
    Printf("%zu bytes inside of", offset);
  } else if (chunk.AddrIsAtLeft(addr, access_size, &offset)) {
    Printf("%zu bytes to the left of", offset);
  } else if (chunk.AddrIsAtRight(addr, access_size, &offset)) {
    Printf("%zu bytes to the right of", offset);
  } else {
    Printf(" somewhere around (this is AddressSanitizer bug!)");
  }
  Printf(" %zu-byte region [%p,%p)\n", chunk.UsedSize(),
         (void*)(chunk.Beg()), (void*)(chunk.End()));
}

void DescribeHeapAddress(uptr addr, uptr access_size) {
  AsanChunkView chunk = FindHeapChunkByAddress(addr);
  if (!chunk.IsValid()) return;
  DescribeAccessToHeapChunk(chunk, addr, access_size);
  CHECK(chunk.AllocTid() != kInvalidTid);
  AsanThreadSummary *alloc_thread =
      asanThreadRegistry().FindByTid(chunk.AllocTid());
  StackTrace alloc_stack;
  chunk.GetAllocStack(&alloc_stack);
  AsanThread *t = asanThreadRegistry().GetCurrent();
  CHECK(t);
  if (chunk.FreeTid() != kInvalidTid) {
    AsanThreadSummary *free_thread =
        asanThreadRegistry().FindByTid(chunk.FreeTid());
    Printf("freed by thread T%d here:\n", free_thread->tid());
    StackTrace free_stack;
    chunk.GetFreeStack(&free_stack);
    PrintStack(&free_stack);
    Printf("previously allocated by thread T%d here:\n", alloc_thread->tid());
    PrintStack(&alloc_stack);
    DescribeThread(t->summary());
    DescribeThread(free_thread);
    DescribeThread(alloc_thread);
  } else {
    Printf("allocated by thread T%d here:\n", alloc_thread->tid());
    PrintStack(&alloc_stack);
    DescribeThread(t->summary());
    DescribeThread(alloc_thread);
  }
}

void DescribeAddress(uptr addr, uptr access_size) {
  // Check if this is shadow or shadow gap.
  if (DescribeAddressIfShadow(addr))
    return;
  CHECK(AddrIsInMem(addr));
  if (DescribeAddressIfGlobal(addr))
    return;
  if (DescribeAddressIfStack(addr, access_size))
    return;
  // Assume it is a heap address.
  DescribeHeapAddress(addr, access_size);
}

// ------------------- Thread description -------------------- {{{1

void DescribeThread(AsanThreadSummary *summary) {
  CHECK(summary);
  // No need to announce the main thread.
  if (summary->tid() == 0 || summary->announced()) {
    return;
  }
  summary->set_announced(true);
  Printf("Thread T%d created by T%d here:\n",
         summary->tid(), summary->parent_tid());
  PrintStack(summary->stack());
  // Recursively described parent thread if needed.
  if (flags()->print_full_thread_history) {
    AsanThreadSummary *parent_summary =
        asanThreadRegistry().FindByTid(summary->parent_tid());
    DescribeThread(parent_summary);
  }
}

// -------------------- Different kinds of reports ----------------- {{{1

// Use ScopedInErrorReport to run common actions just before and
// immediately after printing error report.
class ScopedInErrorReport {
 public:
  ScopedInErrorReport() {
    static atomic_uint32_t num_calls;
    static u32 reporting_thread_tid;
    if (atomic_fetch_add(&num_calls, 1, memory_order_relaxed) != 0) {
      // Do not print more than one report, otherwise they will mix up.
      // Error reporting functions shouldn't return at this situation, as
      // they are defined as no-return.
      Report("AddressSanitizer: while reporting a bug found another one."
                 "Ignoring.\n");
      u32 current_tid = asanThreadRegistry().GetCurrentTidOrInvalid();
      if (current_tid != reporting_thread_tid) {
        // ASan found two bugs in different threads simultaneously. Sleep
        // long enough to make sure that the thread which started to print
        // an error report will finish doing it.
        SleepForSeconds(Max(100, flags()->sleep_before_dying + 1));
      }
      Die();
    }
    __asan_on_error();
    reporting_thread_tid = asanThreadRegistry().GetCurrentTidOrInvalid();
    Printf("===================================================="
           "=============\n");
    if (reporting_thread_tid != kInvalidTid) {
      // We started reporting an error message. Stop using the fake stack
      // in case we call an instrumented function from a symbolizer.
      AsanThread *curr_thread = asanThreadRegistry().GetCurrent();
      CHECK(curr_thread);
      curr_thread->fake_stack().StopUsingFakeStack();
    }
  }
  // Destructor is NORETURN, as functions that report errors are.
  NORETURN ~ScopedInErrorReport() {
    // Make sure the current thread is announced.
    AsanThread *curr_thread = asanThreadRegistry().GetCurrent();
    if (curr_thread) {
      DescribeThread(curr_thread->summary());
    }
    // Print memory stats.
    __asan_print_accumulated_stats();
    if (error_report_callback) {
      error_report_callback(error_message_buffer);
    }
    Report("ABORTING\n");
    Die();
  }
};

void ReportSIGSEGV(uptr pc, uptr sp, uptr bp, uptr addr) {
  ScopedInErrorReport in_report;
  Report("ERROR: AddressSanitizer crashed on unknown address %p"
             " (pc %p sp %p bp %p T%d)\n",
             (void*)addr, (void*)pc, (void*)sp, (void*)bp,
             asanThreadRegistry().GetCurrentTidOrInvalid());
  Printf("AddressSanitizer can not provide additional info.\n");
  GET_STACK_TRACE_WITH_PC_AND_BP(kStackTraceMax, pc, bp);
  PrintStack(&stack);
}

void ReportDoubleFree(uptr addr, StackTrace *stack) {
  ScopedInErrorReport in_report;
  Report("ERROR: AddressSanitizer attempting double-free on %p:\n", addr);
  PrintStack(stack);
  DescribeHeapAddress(addr, 1);
}

void ReportFreeNotMalloced(uptr addr, StackTrace *stack) {
  ScopedInErrorReport in_report;
  Report("ERROR: AddressSanitizer attempting free on address "
             "which was not malloc()-ed: %p\n", addr);
  PrintStack(stack);
  DescribeHeapAddress(addr, 1);
}

void ReportMallocUsableSizeNotOwned(uptr addr, StackTrace *stack) {
  ScopedInErrorReport in_report;
  Report("ERROR: AddressSanitizer attempting to call "
             "malloc_usable_size() for pointer which is "
             "not owned: %p\n", addr);
  PrintStack(stack);
  DescribeHeapAddress(addr, 1);
}

void ReportAsanGetAllocatedSizeNotOwned(uptr addr, StackTrace *stack) {
  ScopedInErrorReport in_report;
  Report("ERROR: AddressSanitizer attempting to call "
             "__asan_get_allocated_size() for pointer which is "
             "not owned: %p\n", addr);
  PrintStack(stack);
  DescribeHeapAddress(addr, 1);
}

void ReportStringFunctionMemoryRangesOverlap(
    const char *function, const char *offset1, uptr length1,
    const char *offset2, uptr length2, StackTrace *stack) {
  ScopedInErrorReport in_report;
  Report("ERROR: AddressSanitizer %s-param-overlap: "
             "memory ranges [%p,%p) and [%p, %p) overlap\n", \
             function, offset1, offset1 + length1, offset2, offset2 + length2);
  PrintStack(stack);
  DescribeAddress((uptr)offset1, length1);
  DescribeAddress((uptr)offset2, length2);
}

// ----------------------- Mac-specific reports ----------------- {{{1

void WarnMacFreeUnallocated(
    uptr addr, uptr zone_ptr, const char *zone_name, StackTrace *stack) {
  // Just print a warning here.
  Printf("free_common(%p) -- attempting to free unallocated memory.\n"
             "AddressSanitizer is ignoring this error on Mac OS now.\n",
             addr);
  PrintZoneForPointer(addr, zone_ptr, zone_name);
  PrintStack(stack);
  DescribeHeapAddress(addr, 1);
}

void ReportMacMzReallocUnknown(
    uptr addr, uptr zone_ptr, const char *zone_name, StackTrace *stack) {
  ScopedInErrorReport in_report;
  Printf("mz_realloc(%p) -- attempting to realloc unallocated memory.\n"
             "This is an unrecoverable problem, exiting now.\n",
             addr);
  PrintZoneForPointer(addr, zone_ptr, zone_name);
  PrintStack(stack);
  DescribeHeapAddress(addr, 1);
}

void ReportMacCfReallocUnknown(
    uptr addr, uptr zone_ptr, const char *zone_name, StackTrace *stack) {
  ScopedInErrorReport in_report;
  Printf("cf_realloc(%p) -- attempting to realloc unallocated memory.\n"
             "This is an unrecoverable problem, exiting now.\n",
             addr);
  PrintZoneForPointer(addr, zone_ptr, zone_name);
  PrintStack(stack);
  DescribeHeapAddress(addr, 1);
}

}  // namespace __asan

// --------------------------- Interface --------------------- {{{1
using namespace __asan;  // NOLINT

void __asan_report_error(uptr pc, uptr bp, uptr sp,
                         uptr addr, bool is_write, uptr access_size) {
  ScopedInErrorReport in_report;

  // Determine the error type.
  const char *bug_descr = "unknown-crash";
  if (AddrIsInMem(addr)) {
    u8 *shadow_addr = (u8*)MemToShadow(addr);
    // If we are accessing 16 bytes, look at the second shadow byte.
    if (*shadow_addr == 0 && access_size > SHADOW_GRANULARITY)
      shadow_addr++;
    // If we are in the partial right redzone, look at the next shadow byte.
    if (*shadow_addr > 0 && *shadow_addr < 128)
      shadow_addr++;
    switch (*shadow_addr) {
      case kAsanHeapLeftRedzoneMagic:
      case kAsanHeapRightRedzoneMagic:
        bug_descr = "heap-buffer-overflow";
        break;
      case kAsanHeapFreeMagic:
        bug_descr = "heap-use-after-free";
        break;
      case kAsanStackLeftRedzoneMagic:
        bug_descr = "stack-buffer-underflow";
        break;
      case kAsanInitializationOrderMagic:
        bug_descr = "initialization-order-fiasco";
        break;
      case kAsanStackMidRedzoneMagic:
      case kAsanStackRightRedzoneMagic:
      case kAsanStackPartialRedzoneMagic:
        bug_descr = "stack-buffer-overflow";
        break;
      case kAsanStackAfterReturnMagic:
        bug_descr = "stack-use-after-return";
        break;
      case kAsanUserPoisonedMemoryMagic:
        bug_descr = "use-after-poison";
        break;
      case kAsanGlobalRedzoneMagic:
        bug_descr = "global-buffer-overflow";
        break;
    }
  }

  Report("ERROR: AddressSanitizer %s on address "
             "%p at pc 0x%zx bp 0x%zx sp 0x%zx\n",
             bug_descr, (void*)addr, pc, bp, sp);

  u32 curr_tid = asanThreadRegistry().GetCurrentTidOrInvalid();
  Printf("%s of size %zu at %p thread T%d\n",
             access_size ? (is_write ? "WRITE" : "READ") : "ACCESS",
             access_size, (void*)addr, curr_tid);

  GET_STACK_TRACE_WITH_PC_AND_BP(kStackTraceMax, pc, bp);
  PrintStack(&stack);

  DescribeAddress(addr, access_size);

  PrintShadowMemoryForAddress(addr);
}

void NOINLINE __asan_set_error_report_callback(void (*callback)(const char*)) {
  error_report_callback = callback;
  if (callback) {
    error_message_buffer_size = 1 << 16;
    error_message_buffer =
        (char*)MmapOrDie(error_message_buffer_size, __FUNCTION__);
    error_message_buffer_pos = 0;
  }
}

// Provide default implementation of __asan_on_error that does nothing
// and may be overriden by user.
SANITIZER_WEAK_ATTRIBUTE SANITIZER_INTERFACE_ATTRIBUTE NOINLINE
void __asan_on_error() {}