libutils: Fix integer overflows in VectorImpl.
Use external/safe-iop to check for overflows on arithmetic
operations.
Also remove an unnecessary copy of Vector/SharedBuffer from
codeflinger and use the copy from libutils instead.
Note that some of the unit tests are somewhat useless due to
test-runner limitations : gtest's ability to filter on abort message
doesn't work when combined with messages formatted by android's logging
system.
bug: 22953624
Change-Id: I46b1ae8ca1f3a010be13aca36a091e76a97a7b70
diff --git a/libutils/VectorImpl.cpp b/libutils/VectorImpl.cpp
index 30ca663..de65a6c 100644
--- a/libutils/VectorImpl.cpp
+++ b/libutils/VectorImpl.cpp
@@ -21,6 +21,7 @@
#include <stdio.h>
#include <cutils/log.h>
+#include <safe_iop.h>
#include <utils/Errors.h>
#include <utils/SharedBuffer.h>
@@ -85,14 +86,19 @@
void* VectorImpl::editArrayImpl()
{
if (mStorage) {
- SharedBuffer* sb = SharedBuffer::bufferFromData(mStorage)->attemptEdit();
- if (sb == 0) {
- sb = SharedBuffer::alloc(capacity() * mItemSize);
- if (sb) {
- _do_copy(sb->data(), mStorage, mCount);
- release_storage();
- mStorage = sb->data();
- }
+ const SharedBuffer* sb = SharedBuffer::bufferFromData(mStorage);
+ SharedBuffer* editable = sb->attemptEdit();
+ if (editable == 0) {
+ // If we're here, we're not the only owner of the buffer.
+ // We must make a copy of it.
+ editable = SharedBuffer::alloc(sb->size());
+ // Fail instead of returning a pointer to storage that's not
+ // editable. Otherwise we'd be editing the contents of a buffer
+ // for which we're not the only owner, which is undefined behaviour.
+ LOG_ALWAYS_FATAL_IF(editable == NULL);
+ _do_copy(editable->data(), mStorage, mCount);
+ release_storage();
+ mStorage = editable->data();
}
}
return mStorage;
@@ -325,13 +331,15 @@
ssize_t VectorImpl::setCapacity(size_t new_capacity)
{
- size_t current_capacity = capacity();
- ssize_t amount = new_capacity - size();
- if (amount <= 0) {
- // we can't reduce the capacity
- return current_capacity;
- }
- SharedBuffer* sb = SharedBuffer::alloc(new_capacity * mItemSize);
+ // The capacity must always be greater than or equal to the size
+ // of this vector.
+ if (new_capacity <= size()) {
+ return capacity();
+ }
+
+ size_t new_allocation_size = 0;
+ LOG_ALWAYS_FATAL_IF(!safe_mul(&new_allocation_size, new_capacity, mItemSize));
+ SharedBuffer* sb = SharedBuffer::alloc(new_allocation_size);
if (sb) {
void* array = sb->data();
_do_copy(array, mStorage, size());
@@ -373,9 +381,28 @@
"[%p] _grow: where=%d, amount=%d, count=%d",
this, (int)where, (int)amount, (int)mCount); // caller already checked
- const size_t new_size = mCount + amount;
+ size_t new_size;
+ LOG_ALWAYS_FATAL_IF(!safe_add(&new_size, mCount, amount), "new_size overflow");
+
if (capacity() < new_size) {
- const size_t new_capacity = max(kMinVectorCapacity, ((new_size*3)+1)/2);
+ // NOTE: This implementation used to resize vectors as per ((3*x + 1) / 2)
+ // (sigh..). Also note, the " + 1" was necessary to handle the special case
+ // where x == 1, where the resized_capacity will be equal to the old
+ // capacity without the +1. The old calculation wouldn't work properly
+ // if x was zero.
+ //
+ // This approximates the old calculation, using (x + (x/2) + 1) instead.
+ size_t new_capacity = 0;
+ LOG_ALWAYS_FATAL_IF(!safe_add(&new_capacity, new_size, (new_size / 2)),
+ "new_capacity overflow");
+ LOG_ALWAYS_FATAL_IF(!safe_add(&new_capacity, new_capacity, static_cast<size_t>(1u)),
+ "new_capacity overflow");
+ new_capacity = max(kMinVectorCapacity, new_capacity);
+
+ size_t new_alloc_size = 0;
+ LOG_ALWAYS_FATAL_IF(!safe_mul(&new_alloc_size, new_capacity, mItemSize),
+ "new_alloc_size overflow");
+
// ALOGV("grow vector %p, new_capacity=%d", this, (int)new_capacity);
if ((mStorage) &&
(mCount==where) &&
@@ -383,14 +410,14 @@
(mFlags & HAS_TRIVIAL_DTOR))
{
const SharedBuffer* cur_sb = SharedBuffer::bufferFromData(mStorage);
- SharedBuffer* sb = cur_sb->editResize(new_capacity * mItemSize);
+ SharedBuffer* sb = cur_sb->editResize(new_alloc_size);
if (sb) {
mStorage = sb->data();
} else {
return NULL;
}
} else {
- SharedBuffer* sb = SharedBuffer::alloc(new_capacity * mItemSize);
+ SharedBuffer* sb = SharedBuffer::alloc(new_alloc_size);
if (sb) {
void* array = sb->data();
if (where != 0) {
@@ -432,10 +459,19 @@
"[%p] _shrink: where=%d, amount=%d, count=%d",
this, (int)where, (int)amount, (int)mCount); // caller already checked
- const size_t new_size = mCount - amount;
- if (new_size*3 < capacity()) {
- const size_t new_capacity = max(kMinVectorCapacity, new_size*2);
-// ALOGV("shrink vector %p, new_capacity=%d", this, (int)new_capacity);
+ size_t new_size;
+ LOG_ALWAYS_FATAL_IF(!safe_sub(&new_size, mCount, amount));
+
+ if (new_size < (capacity() / 2)) {
+ // NOTE: (new_size * 2) is safe because capacity didn't overflow and
+ // new_size < (capacity / 2)).
+ const size_t new_capacity = max(kMinVectorCapacity, new_size * 2);
+
+ // NOTE: (new_capacity * mItemSize), (where * mItemSize) and
+ // ((where + amount) * mItemSize) beyond this point are safe because
+ // we are always reducing the capacity of the underlying SharedBuffer.
+ // In other words, (old_capacity * mItemSize) did not overflow, and
+ // where < (where + amount) < new_capacity < old_capacity.
if ((where == new_size) &&
(mFlags & HAS_TRIVIAL_COPY) &&
(mFlags & HAS_TRIVIAL_DTOR))