TCMalloc: restrict maximum size of memory ranges

base/security_unittest.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.

[Chris Evans, 2013/01/15 01:53:08]

2013

[jln (very slow on Chromium), 2013/01/15 02:00:51]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <algorithm>
+#include <limits>
+
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using std::nothrow;
+
+namespace {
+
+// Check that we can not allocate a memory range that cannot be indexed
+// via an int. This is used to mitigate vulnerabilities in libraries that use
+// int instead of size_t.
+// See crbug.com/169327.
+
+// - NO_TCMALLOC because we only patched tcmalloc
+// - ADDRESS_SANITIZER because it has its own memory allocator
+// - IOS does not seem to honor nothrow in new properly
+// - OS_MACOSX does not use tcmalloc
+#if !defined(NO_TCMALLOC) && !defined(ADDRESS_SANITIZER) && \
+    !defined(OS_IOS) && !defined(OS_MACOSX)
+  #define ALLOC_TEST(function) function
+#else
+  #define ALLOC_TEST(function) DISABLED_##function
+#endif
+
+// TODO(jln): switch to std::numeric_limits<int>::max() when we switch to
+// C++11.
+const size_t kMaxAllocSize = INT_MAX;
+
+// Detect runtime TCMalloc bypasses.
+bool IsTcMallocBypassed() {
+#if defined(OS_LINUX)
+  // This should detect a TCMalloc bypass from Valgrind.
+  char* g_slice = getenv("G_SLICE");
+  if (g_slice && !strcmp(g_slice, "always-malloc"))
+    return true;
+#endif
+  return false;
+}
+
+// Fake test that allow to know the state of TCMalloc by looking at bots.
+TEST(SecurityTest, ALLOC_TEST(IsTCMallocDynamicallyBypassed)) {
+  printf("Malloc is dynamically bypassed: %s\n",
+         IsTcMallocBypassed() ? "yes." : "no.");
+}
+
+TEST(SecurityTest, ALLOC_TEST(MemoryAllocationRestrictionsMalloc)) {
+  if (!IsTcMallocBypassed()) {
+    scoped_ptr<char, base::FreeDeleter>
+        ptr(static_cast<char*>(malloc(kMaxAllocSize)));

[Chris Evans, 2013/01/15 01:53:08]

It's weird to have a test that "kMaxAllocSize" actually fails (because of the
page_size accounting tweak I know). Maybe call it kTooBigAllocSize ?

[jln (very slow on Chromium), 2013/01/15 02:00:51]

Good point, done.

+  ASSERT_TRUE(ptr == NULL);

[Chris Evans, 2013/01/15 01:53:08]

Indentation.

[Chris Evans, 2013/01/15 01:53:08]

Indentation

[jln (very slow on Chromium), 2013/01/15 02:00:51]

Done.

+  }
+}
+
+TEST(SecurityTest, ALLOC_TEST(MemoryAllocationRestrictionsCalloc)) {
+  if (!IsTcMallocBypassed()) {
+    scoped_ptr<char, base::FreeDeleter>
+        ptr(static_cast<char*>(calloc(kMaxAllocSize, 1)));
+    ASSERT_TRUE(ptr == NULL);
+  }
+}
+
+TEST(SecurityTest, ALLOC_TEST(MemoryAllocationRestrictionsRealloc)) {
+  if (!IsTcMallocBypassed()) {
+    char* orig_ptr = static_cast<char*>(malloc(1));
+    ASSERT_TRUE(orig_ptr != NULL);
+    scoped_ptr<char, base::FreeDeleter>
+        ptr(static_cast<char*>(realloc(orig_ptr, kMaxAllocSize)));
+    ASSERT_TRUE(ptr == NULL);
+    // If realloc() did not succeed, we need to free orig_ptr.
+    free(orig_ptr);
+  }
+}
+
+typedef struct {
+  char large_array[kMaxAllocSize];
+} VeryLargeStruct;
+
+TEST(SecurityTest, ALLOC_TEST(MemoryAllocationRestrictionsNew)) {
+  if (!IsTcMallocBypassed()) {
+    scoped_ptr<VeryLargeStruct> ptr(new (nothrow) VeryLargeStruct);
+    ASSERT_TRUE(ptr == NULL);
+  }
+}
+
+TEST(SecurityTest, ALLOC_TEST(MemoryAllocationRestrictionsNewArray)) {
+  if (!IsTcMallocBypassed()) {
+    scoped_array<char> ptr(new (nothrow) char[kMaxAllocSize]);
+    ASSERT_TRUE(ptr == NULL);
+  }
+}
+
+// This would be a test for a much stricter restriction preventing a contiguous
+// memory area of size MaximumAllocSize to be allocated via malloc.
+// Implementing this requires more effort and the test is disabled.

[Chris Evans, 2013/01/15 01:53:08]

I think we're better off not landing to be honest?

[jln (very slow on Chromium), 2013/01/15 02:00:51]

Done.

+TEST(SecurityTest, DISABLED_MemoryAllocationRestrictionsStepped) {
+  const int kAllocNumber = 8;
+  const size_t kSteppedAllocSize = kMaxAllocSize / kAllocNumber;
+  // Allow 1/32th for MetaData and padding.
+  const size_t kExpectedExtra = kSteppedAllocSize >> 5;
+
+  bool is_contiguous = true;
+  // Make kAllocNumber successive allocations and compare the successive
+  // pointers to detect adjacent mappings.
+  scoped_ptr<char, base::FreeDeleter> ptr[kAllocNumber];
+  for (int i = 0; i < kAllocNumber; ++i) {
+    ptr[i].reset(static_cast<char*>(malloc(kSteppedAllocSize)));
+    if (ptr[i] == NULL) {
+      is_contiguous = false;
+      break;
+    }
+    if (i > 0) {
+      size_t pointer_diff = static_cast<size_t>(
+          std::max(ptr[i].get(), ptr[i - 1].get()) -
+          std::min(ptr[i].get(), ptr[i - 1].get()));
+      if (pointer_diff > (kSteppedAllocSize + kExpectedExtra)) {
+        is_contiguous = false;
+        break;
+      }
+    }
+  }
+  ASSERT_FALSE(is_contiguous);
+}
+
+}  // namespace