libutils: fix overflow in SharedBuffer [DO NOT MERGE]

See
https://code.google.com/p/android/issues/detail?id=181910

Bug: 22952485
(cherry picked from commit 66b6eb9490)

Change-Id: I363f49b5b3c6b7b3ac08cba2c14d72c431588c5a

libutils/Android.mk

@@ -108,6 +108,22 @@ LOCAL_CFLAGS := -Werror
 
 include $(BUILD_SHARED_LIBRARY)
 
+# Include subdirectory makefiles
+# ============================================================
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := SharedBufferTest
+LOCAL_STATIC_LIBRARIES := libutils libcutils
+LOCAL_SHARED_LIBRARIES := liblog
+LOCAL_SRC_FILES := SharedBufferTest.cpp
+include $(BUILD_NATIVE_TEST)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := SharedBufferTest
+LOCAL_STATIC_LIBRARIES := libutils libcutils
+LOCAL_SHARED_LIBRARIES := liblog
+LOCAL_SRC_FILES := SharedBufferTest.cpp
+include $(BUILD_HOST_NATIVE_TEST)
 
 # Build the tests in the tests/ subdirectory.
 include $(call first-makefiles-under,$(LOCAL_PATH))

libutils/SharedBuffer.cpp

@@ -14,9 +14,12 @@
  * limitations under the License.
  */
 
+#define __STDC_LIMIT_MACROS
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include <log/log.h>
 #include <utils/SharedBuffer.h>
 #include <utils/Atomic.h>
 
@@ -26,6 +29,11 @@ namespace android {
 
 SharedBuffer* SharedBuffer::alloc(size_t size)
 {
+    // Don't overflow if the combined size of the buffer / header is larger than
+    // size_max.
+    LOG_ALWAYS_FATAL_IF((size >= (SIZE_MAX - sizeof(SharedBuffer))),
+                        "Invalid buffer size %zu", size);
+
     SharedBuffer* sb = static_cast<SharedBuffer *>(malloc(sizeof(SharedBuffer) + size));
     if (sb) {
         sb->mRefs = 1;
@@ -52,7 +60,7 @@ SharedBuffer* SharedBuffer::edit() const
         memcpy(sb->data(), data(), size());
         release();
     }
-    return sb;    
+    return sb;
 }
 
 SharedBuffer* SharedBuffer::editResize(size_t newSize) const
@@ -60,6 +68,11 @@ SharedBuffer* SharedBuffer::editResize(size_t newSize) const
     if (onlyOwner()) {
         SharedBuffer* buf = const_cast<SharedBuffer*>(this);
         if (buf->mSize == newSize) return buf;
+        // Don't overflow if the combined size of the new buffer / header is larger than
+        // size_max.
+        LOG_ALWAYS_FATAL_IF((newSize >= (SIZE_MAX - sizeof(SharedBuffer))),
+                            "Invalid buffer size %zu", newSize);
+
         buf = (SharedBuffer*)realloc(buf, sizeof(SharedBuffer) + newSize);
         if (buf != NULL) {
             buf->mSize = newSize;

libutils/SharedBufferTest.cpp

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define __STDC_LIMIT_MACROS
+
+#include <utils/SharedBuffer.h>
+
+#include <gtest/gtest.h>
+
+#include <memory>
+#include <stdint.h>
+
+TEST(SharedBufferTest, TestAlloc) {
+  EXPECT_DEATH(android::SharedBuffer::alloc(SIZE_MAX), "");
+  EXPECT_DEATH(android::SharedBuffer::alloc(SIZE_MAX - sizeof(android::SharedBuffer)), "");
+
+  // Make sure we don't die here.
+  // Check that null is returned, as we are asking for the whole address space.
+  android::SharedBuffer* buf =
+      android::SharedBuffer::alloc(SIZE_MAX - sizeof(android::SharedBuffer) - 1);
+  ASSERT_TRUE(NULL == buf);
+
+  buf = android::SharedBuffer::alloc(0);
+  ASSERT_FALSE(NULL == buf);
+  ASSERT_EQ(0U, buf->size());
+  buf->release();
+}
+
+TEST(SharedBufferTest, TestEditResize) {
+  android::SharedBuffer* buf = android::SharedBuffer::alloc(10);
+  EXPECT_DEATH(buf->editResize(SIZE_MAX - sizeof(android::SharedBuffer)), "");
+  buf = android::SharedBuffer::alloc(10);
+  EXPECT_DEATH(buf->editResize(SIZE_MAX), "");
+
+  buf = android::SharedBuffer::alloc(10);
+  // Make sure we don't die here.
+  // Check that null is returned, as we are asking for the whole address space.
+  buf = buf->editResize(SIZE_MAX - sizeof(android::SharedBuffer) - 1);
+  ASSERT_TRUE(NULL == buf);
+
+  buf = android::SharedBuffer::alloc(10);
+  buf = buf->editResize(0);
+  ASSERT_EQ(0U, buf->size());
+  buf->release();
+}