[GWP-ASan] Integration with Scudo [5].

[hctim]

Summary

See D60593 for further information.

This patch adds GWP-ASan support to the Scudo hardened allocator. It also
implements end-to-end integration tests using Scudo as the backing allocator.
The tests include crash handling for buffer over/underflow as well as
use-after-free detection.

[cryptoad]

I think it's good from the integration perspective.
The only potential concern I have is the specific use of the TLS variables in GWP-ASan which might not work everywhere here (eg: if a platform is using emutls as TLS as it uses malloc() internally).
Have you tested that locally with an Android emulator?

compiler-rt/test/scudo/lit.cfg

54

nit: do you need the extra variable?

[hctim]

In D62929#1531586, @cryptoad wrote:

The only potential concern I have is the specific use of the TLS variables in GWP-ASan which might not work everywhere here (eg: if a platform is using emutls as TLS as it uses malloc() internally).

GWP-ASan is not supported on platforms without initial exec TLS, and won't build there -- in which case, it won't be included in Scudo :)

Have you tested that locally with an Android emulator?

Not as of right now, but Q will support ELF TLS instead of emutls (https://developer.android.com/preview/features#elf-tls). Will take a look at this soon.

[hctim]

• Removed extra var in scudo lit cfg.

[vlad.tsyrklevich]

compiler-rt/lib/scudo/scudo_allocator.cpp

493

Just checking, does reallocate() have the same semantics as realloc() where NewSize == 0 means free? And does allocate(0) always return nullptr in that case?

compiler-rt/test/gwp_asan/invalid_free_left.cpp

4

This uses not while the others above use %expect_crash, you probably want %expect_crash here too and in the other places you use not?

[hctim]

• Added new realloc test, deleted dummy test.

compiler-rt/lib/scudo/scudo_allocator.cpp

493

Yep - have also added a unit test for this. Note that C++11 changed this behaviour, and made it implementation defined.

compiler-rt/test/gwp_asan/invalid_free_left.cpp

4

So at the moment, invalid free/double free are detected internally, and terminate through exit(EXIT_FAILURE). The tests with %expect_crash are the ones which terminate through a segv signal ($? == 127).

This is mirroring the behaviour of scudo, where they exit(EXIT_FAILURE) on checksum failure or other error conditions. What might be better though, is when we detect a failure condition internally, we raise a signal. This would allow platforms like Android to still have their special death handlers run.

@morehouse - WDYT? I would say that I'd prefer to raise a signal internally-detected error. I'm not sure that raising SEGV is appropriate here, and it would also increase the complexity of the logic (we'd have to reinstate the previous SEGV handler first). Maybe SIGTRAP or SIGABRT?

[morehouse]

compiler-rt/test/gwp_asan/invalid_free_left.cpp

4

FWIW, we trigger a SEGV in Google3 by touching the freed page. Not sure if it's the best approach, but it simplified the error handling a bit. Allows everything to go through SEGV handler and then forward to the previous handers, rather than having to implement multiple flows for different errors. Also gives the address of the double-free to previous handlers for them to inspect.

[hctim]

Merge master in preparation for submit.

compiler-rt/lib/scudo/CMakeLists.txt

# android-changes-for-ndk-developers.md#changes-to-library-search-order
   endif()
 endif()
 
 # The minimal Scudo runtime does not inlude the UBSan runtime.
 set(SCUDO_MINIMAL_OBJECT_LIBS
   RTSanitizerCommonNoTermination
   RTSanitizerCommonLibc
   RTInterception)
+
+if (COMPILER_RT_HAS_GWP_ASAN)
+  # Currently, Scudo uses the GwpAsan flag parser. This backs onto the flag
+  # parsing mechanism of sanitizer_common. Once Scudo has its own flag parsing,
+  # and parses GwpAsan options, you can remove this dependency.
+  list(APPEND SCUDO_MINIMAL_OBJECT_LIBS RTGwpAsan RTGwpAsanOptionsParser)
+  list(APPEND SCUDO_CFLAGS -DGWP_ASAN_HOOKS)
+endif()
+
 set(SCUDO_OBJECT_LIBS ${SCUDO_MINIMAL_OBJECT_LIBS})
 set(SCUDO_DYNAMIC_LIBS ${SCUDO_MINIMAL_DYNAMIC_LIBS})
 
 if (FUCHSIA)
   list(APPEND SCUDO_CFLAGS -nostdinc++)
   list(APPEND SCUDO_DYNAMIC_LINK_FLAGS -nostdlib++)
 else()
   list(APPEND SCUDO_DYNAMIC_LIBS ${SANITIZER_CXX_ABI_LIBRARIES})

compiler-rt/lib/scudo/scudo_allocator.cpp

 #include "scudo_interface_internal.h"
 #include "scudo_tsd.h"
 #include "scudo_utils.h"
 
 #include "sanitizer_common/sanitizer_allocator_checks.h"
 #include "sanitizer_common/sanitizer_allocator_interface.h"
 #include "sanitizer_common/sanitizer_quarantine.h"
 
+#ifdef GWP_ASAN_HOOKS
+# include "gwp_asan/guarded_pool_allocator.h"
+# include "gwp_asan/optional/options_parser.h"
+#endif // GWP_ASAN_HOOKS
+
 #include <errno.h>
 #include <string.h>
 
 namespace __scudo {
 
 // Global static cookie, initialized at start-up.
 static u32 Cookie;
 

 typedef QuarantineT::Cache QuarantineCacheT;
 COMPILER_CHECK(sizeof(QuarantineCacheT) <=
                sizeof(ScudoTSD::QuarantineCachePlaceHolder));
 
 QuarantineCacheT *getQuarantineCache(ScudoTSD *TSD) {
   return reinterpret_cast<QuarantineCacheT *>(TSD->QuarantineCachePlaceHolder);
 }
 
+#ifdef GWP_ASAN_HOOKS
+static gwp_asan::GuardedPoolAllocator GuardedAlloc;
+#endif // GWP_ASAN_HOOKS
+
 struct Allocator {
   static const uptr MaxAllowedMallocSize =
       FIRST_32_SECOND_64(2UL << 30, 1ULL << 40);
 
   BackendT Backend;
   QuarantineT Quarantine;
 
   u32 QuarantineChunksUpToSize;
struct Allocator {
   }
 
   NOINLINE bool isRssLimitExceeded();
 
   // Allocates a chunk.
   void *allocate(uptr Size, uptr Alignment, AllocType Type,
                  bool ForceZeroContents = false) {
     initThreadMaybe();
+
+#ifdef GWP_ASAN_HOOKS
+    if (UNLIKELY(GuardedAlloc.shouldSample())) {
+      if (void *Ptr = GuardedAlloc.allocate(Size))
+        return Ptr;
+    }
+#endif // GWP_ASAN_HOOKS
+
     if (UNLIKELY(Alignment > MaxAlignment)) {
       if (AllocatorMayReturnNull())
         return nullptr;
       reportAllocationAlignmentTooBig(Alignment, MaxAlignment);
     }
     if (UNLIKELY(Alignment < MinAlignment))
       Alignment = MinAlignment;
 
void deallocate(void *Ptr, uptr DeleteSize, uptr DeleteAlignment,
     // where the only heap operation performed in a thread would be a free past
     // the TLS destructors, ending up in initialized thread specific data never
     // being destroyed properly. Any other heap operation will do a full init.
     initThreadMaybe(/*MinimalInit=*/true);
     if (SCUDO_CAN_USE_HOOKS && &__sanitizer_free_hook)
       __sanitizer_free_hook(Ptr);
     if (UNLIKELY(!Ptr))
       return;
+
+#ifdef GWP_ASAN_HOOKS
+    if (UNLIKELY(GuardedAlloc.pointerIsMine(Ptr))) {
+      GuardedAlloc.deallocate(Ptr);
+      return;
+    }
+#endif // GWP_ASAN_HOOKS
+
     if (UNLIKELY(!Chunk::isAligned(Ptr)))
       dieWithMessage("misaligned pointer when deallocating address %p\n", Ptr);
     UnpackedHeader Header;
     Chunk::loadHeader(Ptr, &Header);
     if (UNLIKELY(Header.State != ChunkAllocated))
       dieWithMessage("invalid chunk state when deallocating address %p\n", Ptr);
     if (DeallocationTypeMismatch) {
       // The deallocation type has to match the allocation one.
#endif // GWP_ASAN_HOOKS
     (void)DeleteAlignment;  // TODO(kostyak): verify that the alignment matches.
     quarantineOrDeallocateChunk(Ptr, &Header, Size);
   }
 
   // Reallocates a chunk. We can save on a new allocation if the new requested
   // size still fits in the chunk.
   void *reallocate(void *OldPtr, uptr NewSize) {
     initThreadMaybe();
+
+#ifdef GWP_ASAN_HOOKS
+    if (UNLIKELY(GuardedAlloc.pointerIsMine(OldPtr))) {
+      size_t OldSize = GuardedAlloc.getSize(OldPtr);
+      void *NewPtr = allocate(NewSize, MinAlignment, FromMalloc);
+      if (NewPtr)
+        memcpy(NewPtr, OldPtr, (NewSize < OldSize) ? NewSize : OldSize);
+      GuardedAlloc.deallocate(OldPtr);
+      return NewPtr;
+    }
+#endif // GWP_ASAN_HOOKS
+
     if (UNLIKELY(!Chunk::isAligned(OldPtr)))
       dieWithMessage("misaligned address when reallocating address %p\n",
                      OldPtr);
     UnpackedHeader OldHeader;
     Chunk::loadHeader(OldPtr, &OldHeader);
     if (UNLIKELY(OldHeader.State != ChunkAllocated))
       dieWithMessage("invalid chunk state when reallocating address %p\n",
                      OldPtr);
#endif // GWP_ASAN_HOOKS
     return NewPtr;
   }
 
   // Helper function that returns the actual usable size of a chunk.
   uptr getUsableSize(const void *Ptr) {
     initThreadMaybe();
     if (UNLIKELY(!Ptr))
       return 0;
+
+#ifdef GWP_ASAN_HOOKS
+    if (UNLIKELY(GuardedAlloc.pointerIsMine(Ptr)))
+      return GuardedAlloc.getSize(Ptr);
+#endif // GWP_ASAN_HOOKS
+
     UnpackedHeader Header;
     Chunk::loadHeader(Ptr, &Header);
     // Getting the usable size of a chunk only makes sense if it's allocated.
     if (UNLIKELY(Header.State != ChunkAllocated))
       dieWithMessage("invalid chunk state when sizing address %p\n", Ptr);
     return Chunk::getUsableSize(Ptr, &Header);
   }
 

 static Allocator Instance(LINKER_INITIALIZED);
 
 static BackendT &getBackend() {
   return Instance.Backend;
 }
 
 void initScudo() {
   Instance.init();
+#ifdef GWP_ASAN_HOOKS
+  gwp_asan::options::initOptions();
+  GuardedAlloc.init(gwp_asan::options::getOptions());
+#endif // GWP_ASAN_HOOKS
 }
 
 void ScudoTSD::init() {
   getBackend().initCache(&Cache);
   memset(QuarantineCachePlaceHolder, 0, sizeof(QuarantineCachePlaceHolder));
 }
 
 void ScudoTSD::commitBack() {

compiler-rt/test/gwp_asan/CMakeLists.txt

 set(GWP_ASAN_LIT_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 set(GWP_ASAN_LIT_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
 
 set(GWP_ASAN_TESTSUITES)
 
 set(GWP_ASAN_UNITTEST_DEPS)
 set(GWP_ASAN_TEST_DEPS
   ${SANITIZER_COMMON_LIT_TEST_DEPS}
-  gwp_asan)
+  gwp_asan
+  scudo)
 
 if (COMPILER_RT_INCLUDE_TESTS)
   list(APPEND GWP_ASAN_TEST_DEPS GwpAsanUnitTests)
   configure_lit_site_cfg(
     ${CMAKE_CURRENT_SOURCE_DIR}/unit/lit.site.cfg.in
     ${CMAKE_CURRENT_BINARY_DIR}/unit/lit.site.cfg)
   add_lit_testsuite(check-gwp_asan-unit "Running GWP-ASan unit tests"
     ${CMAKE_CURRENT_BINARY_DIR}/unit

compiler-rt/test/gwp_asan/double_delete.cpp

+// REQUIRES: gwp_asan
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: not %run %t 2>&1 | FileCheck %s
+
+// CHECK: GWP-ASan detected a memory error
+// CHECK: Double free occurred when trying to free memory at:
+
+#include <cstdlib>
+
+int main() {
+  char *Ptr = new char;
+  delete Ptr;
+  delete Ptr;
+  return 0;
+}

compiler-rt/test/gwp_asan/double_deletea.cpp

+// REQUIRES: gwp_asan
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: not %run %t 2>&1 | FileCheck %s
+
+// CHECK: GWP-ASan detected a memory error
+// CHECK: Double free occurred when trying to free memory at:
+
+#include <cstdlib>
+
+int main() {
+  char *Ptr = new char[50];
+  delete[] Ptr;
+  delete[] Ptr;
+  return 0;
+}

compiler-rt/test/gwp_asan/double_free.cpp

+// REQUIRES: gwp_asan
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: not %run %t 2>&1 | FileCheck %s
+
+// CHECK: GWP-ASan detected a memory error
+// CHECK: Double free occurred when trying to free memory at:
+
+#include <cstdlib>
+
+int main() {
+  void *Ptr = malloc(10);
+  free(Ptr);
+  free(Ptr);
+  return 0;
+}

compiler-rt/test/gwp_asan/heap_buffer_overflow.cpp

+// REQUIRES: gwp_asan
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: %expect_crash %run %t 2>&1 | FileCheck %s
+
+// CHECK: GWP-ASan detected a memory error
+// CHECK: Buffer overflow occurred when accessing memory at:
+// CHECK: is located {{[0-9]+}} bytes to the right
+
+#include <cstdlib>
+
+#include "page_size.h"
+
+int main() {
+  char *Ptr =
+      reinterpret_cast<char *>(malloc(pageSize()));
+  volatile char x = *(Ptr + pageSize());
+  return 0;
+}

compiler-rt/test/gwp_asan/heap_buffer_underflow.cpp

+// REQUIRES: gwp_asan
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: %expect_crash %run %t 2>&1 | FileCheck %s
+
+// CHECK: GWP-ASan detected a memory error
+// CHECK: Buffer underflow occurred when accessing memory at:
+// CHECK: is located 1 bytes to the left
+
+#include <cstdlib>
+
+#include "page_size.h"
+
+int main() {
+  char *Ptr =
+      reinterpret_cast<char *>(malloc(pageSize()));
+  volatile char x = *(Ptr - 1);
+  return 0;
+}

compiler-rt/test/gwp_asan/invalid_free_left.cpp

+// REQUIRES: gwp_asan
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: not %run %t 2>&1 | FileCheck %s
+
+// CHECK: GWP-ASan detected a memory error
+// CHECK: Invalid (wild) free occurred when trying to free memory at:
+// CHECK: is located 1 bytes to the left of
+
+#include <cstdlib>
+
+int main() {
+  char *Ptr =
+      reinterpret_cast<char *>(malloc(1));
+  free(Ptr - 1);
+  return 0;
+}

compiler-rt/test/gwp_asan/invalid_free_right.cpp

+// REQUIRES: gwp_asan
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: not %run %t 2>&1 | FileCheck %s
+
+// CHECK: GWP-ASan detected a memory error
+// CHECK: Invalid (wild) free occurred when trying to free memory at:
+// CHECK: is located 1 bytes to the right
+
+#include <cstdlib>
+
+int main() {
+  char *Ptr =
+      reinterpret_cast<char *>(malloc(1));
+  free(Ptr + 1);
+  return 0;
+}

compiler-rt/test/gwp_asan/lit.cfg

 c_flags = ([config.target_cflags])
 
 # Android doesn't want -lrt.
 if not config.android:
   c_flags += ["-lrt"]
 
 cxx_flags = (c_flags + config.cxx_mode_flags + ["-std=c++11"])
 
+gwp_asan_flags = ["-fsanitize=scudo"]
+
 def build_invocation(compile_flags):
   return " " + " ".join([config.clang] + compile_flags) + " "
 
 # Add substitutions.
 config.substitutions.append(("%clang ", build_invocation(c_flags)))
+config.substitutions.append(("%clang_gwp_asan ", build_invocation(c_flags + gwp_asan_flags)))
+config.substitutions.append(("%clangxx_gwp_asan ", build_invocation(cxx_flags + gwp_asan_flags)))
+
+# Platform-specific default GWP_ASAN for lit tests. Ensure that GWP-ASan is
+# enabled and that it samples every allocation.
+default_gwp_asan_options = 'Enabled=1:SampleRate=1'
+
+config.environment['GWP_ASAN_OPTIONS'] = default_gwp_asan_options
+default_gwp_asan_options += ':'
+config.substitutions.append(('%env_gwp_asan_options=',
+                             'env GWP_ASAN_OPTIONS=' + default_gwp_asan_options))
 
 # GWP-ASan tests are currently supported on Linux only.
 if config.host_os not in ['Linux']:
    config.unsupported = True

compiler-rt/test/gwp_asan/page_size.h

+#ifndef PAGE_SIZE_
+#define PAGE_SIZE_
+
+#if defined (__unix__) || (defined (__APPLE__) && defined (__MACH__))
+# include <unistd.h>
+unsigned pageSize() {
+  return sysconf(_SC_PAGESIZE);
+}
+#else
+# error "GWP-ASan is not supported on this platform."
+#endif
+
+#endif // PAGE_SIZE_

compiler-rt/test/gwp_asan/repeated_alloc.cpp

+// REQUIRES: gwp_asan
+// This test ensures that normal allocation/memory access/deallocation works
+// as expected and we didn't accidentally break the supporting allocator.
+
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: %env_gwp_asan_options=MaxSimultaneousAllocations=1 %run %t
+// RUN: %env_gwp_asan_options=MaxSimultaneousAllocations=2 %run %t
+// RUN: %env_gwp_asan_options=MaxSimultaneousAllocations=11 %run %t
+// RUN: %env_gwp_asan_options=MaxSimultaneousAllocations=12 %run %t
+// RUN: %env_gwp_asan_options=MaxSimultaneousAllocations=13 %run %t
+
+#include <cstdlib>
+
+int main() {
+  void* Pointers[16];
+  for (unsigned i = 0; i < 16; ++i) {
+    char *Ptr = reinterpret_cast<char*>(malloc(1 << i));
+    Pointers[i] = Ptr;
+    *Ptr = 0;
+    Ptr[(1 << i) - 1] = 0;
+  }
+
+  for (unsigned i = 0; i < 16; ++i) {
+    free(Pointers[i]);
+  }
+
+  return 0;
+}

compiler-rt/test/gwp_asan/use_after_delete.cpp

+// REQUIRES: gwp_asan
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: %expect_crash %run %t 2>&1 | FileCheck %s
+
+// CHECK: GWP-ASan detected a memory error
+// CHECK: Use after free occurred when accessing memory at:
+
+#include <cstdlib>
+
+int main() {
+  char *Ptr = new char;
+
+  *Ptr = 0x0;
+
+  delete Ptr;
+  volatile char x = *Ptr;
+  return 0;
+}

compiler-rt/test/gwp_asan/use_after_deletea.cpp

+// REQUIRES: gwp_asan
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: %expect_crash %run %t 2>&1 | FileCheck %s
+
+// CHECK: GWP-ASan detected a memory error
+// CHECK: Use after free occurred when accessing memory at:
+
+#include <cstdlib>
+
+int main() {
+  char *Ptr = new char[10];
+
+  for (unsigned i = 0; i < 10; ++i) {
+    *(Ptr + i) = 0x0;
+  }
+
+  delete[] Ptr;
+  volatile char x = *Ptr;
+  return 0;
+}

compiler-rt/test/gwp_asan/use_after_free.cpp

+// REQUIRES: gwp_asan
+// RUN: %clangxx_gwp_asan %s -o %t
+// RUN: %expect_crash %run %t 2>&1 | FileCheck %s
+
+// CHECK: GWP-ASan detected a memory error
+// CHECK: Use after free occurred when accessing memory at:
+
+#include <cstdlib>
+
+int main() {
+  char *Ptr = reinterpret_cast<char *>(malloc(10));
+
+  for (unsigned i = 0; i < 10; ++i) {
+    *(Ptr + i) = 0x0;
+  }
+
+  free(Ptr);
+  volatile char x = *Ptr;
+  return 0;
+}

compiler-rt/test/lit.common.cfg

if config.has_lld:
   config.available_features.add('lld-available')
 
 if config.use_lld:
   config.available_features.add('lld')
 
 if config.can_symbolize:
   config.available_features.add('can-symbolize')
 
+if config.gwp_asan:
+  config.available_features.add('gwp_asan')
+
 lit.util.usePlatformSdkOnDarwin(config, lit_config)
 
 if config.host_os == 'Darwin':
   osx_version = (10, 0, 0)
   try:
     osx_version = subprocess.check_output(["sw_vers", "-productVersion"])
     osx_version = tuple(int(x) for x in osx_version.split('.'))
     if len(osx_version) == 2: osx_version = (osx_version[0], osx_version[1], 0)

compiler-rt/test/lit.common.configured.in

 set_default("use_thinlto", False)
 set_default("use_lto", config.use_thinlto)
 set_default("use_newpm", False)
 set_default("android", @ANDROID_PYBOOL@)
 set_default("android_ndk_version", @ANDROID_NDK_VERSION@)
 set_default("android_serial", "@ANDROID_SERIAL_FOR_TESTING@")
 set_default("android_files_to_push", [])
 set_default("have_rpc_xdr_h", @HAVE_RPC_XDR_H@)
+set_default("gwp_asan", @COMPILER_RT_HAS_GWP_ASAN_PYBOOL@)
 config.available_features.add('target-is-%s' % config.target_arch)
 
 if config.enable_per_target_runtime_dir:
   set_default("target_suffix", "")
 else:
   set_default("target_suffix", "-%s" % config.target_arch)
 
 set_default("have_zlib", "@HAVE_LIBZ@")

compiler-rt/test/scudo/lit.cfg

 config.substitutions.append(("%shared_minlibscudo", shared_minlibscudo))
 
 # Platform-specific default SCUDO_OPTIONS for lit tests.
 default_scudo_opts = ''
 if config.android:
   # Android defaults to abort_on_error=1, which doesn't work for us.
   default_scudo_opts = 'abort_on_error=0'
 
+# Disable GWP-ASan for scudo internal tests.
+if config.gwp_asan:
+  gwp_asan_options = 'Enabled=0'
+  config.environment['GWP_ASAN_OPTIONS'] = gwp_asan_options
+
 if default_scudo_opts:
   config.environment['SCUDO_OPTIONS'] = default_scudo_opts
   default_scudo_opts += ':'
 config.substitutions.append(('%env_scudo_opts=',
                              'env SCUDO_OPTIONS=' + default_scudo_opts))
 
 # Hardened Allocator tests are currently supported on Linux only.
 if config.host_os not in ['Linux']:
    config.unsupported = True