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prevent 32b overflow for very large canvas_width / height

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some multiplies here and there needed some extra checks
and error reporting. Even if width * height is guaranteed
to be < 2**32, we were multiplying by num_channels and
triggering a 32b overflow.
Some multiplies were not using size_t or uint64_t, additionally.

Change-Id: If2a35b94c8af204135f4b88a7fd63850aa381bbf
(cherry picked from commit 1c36440094)
This commit is contained in:
Pascal Massimino 2016-09-23 06:56:11 +02:00 committed by James Zern
parent 9595f29010
commit 3c49178f7d
2 changed files with 43 additions and 23 deletions
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21
examples/anim_util.c
View File

@ -39,13 +39,24 @@ static int IsFullFrame(int width, int height,
return (width == canvas_width && height == canvas_height);
}
static int CheckSizeForOverflow(uint64_t size) {
return (size == (size_t)size);
}
static int AllocateFrames(AnimatedImage* const image, uint32_t num_frames) {
uint32_t i;
const size_t rgba_size =
image->canvas_width * kNumChannels * image->canvas_height;
uint8_t* const mem = (uint8_t*)malloc(num_frames * rgba_size * sizeof(*mem));
DecodedFrame* const frames =
(DecodedFrame*)malloc(num_frames * sizeof(*frames));
uint8_t* mem = NULL;
DecodedFrame* frames = NULL;
const uint64_t rgba_size =
(uint64_t)image->canvas_width * kNumChannels * image->canvas_height;
const uint64_t total_size = (uint64_t)num_frames * rgba_size * sizeof(*mem);
const uint64_t total_frame_size = (uint64_t)num_frames * sizeof(*frames);
if (!CheckSizeForOverflow(total_size) ||
!CheckSizeForOverflow(total_frame_size)) {
return 0;
}
mem = (uint8_t*)malloc(total_size);
frames = (DecodedFrame*)malloc(total_frame_size);
if (mem == NULL || frames == NULL) {
free(mem);

45
src/demux/anim_decode.c
View File

@ -112,18 +112,15 @@ WebPAnimDecoder* WebPAnimDecoderNewInternal(
dec->info_.bgcolor = WebPDemuxGetI(dec->demux_, WEBP_FF_BACKGROUND_COLOR);
dec->info_.frame_count = WebPDemuxGetI(dec->demux_, WEBP_FF_FRAME_COUNT);
{
const int canvas_bytes =
dec->info_.canvas_width * NUM_CHANNELS * dec->info_.canvas_height;
// Note: calloc() because we fill frame with zeroes as well.
dec->curr_frame_ = WebPSafeCalloc(1ULL, canvas_bytes);
if (dec->curr_frame_ == NULL) goto Error;
dec->prev_frame_disposed_ = WebPSafeCalloc(1ULL, canvas_bytes);
if (dec->prev_frame_disposed_ == NULL) goto Error;
}
// Note: calloc() because we fill frame with zeroes as well.
dec->curr_frame_ = WebPSafeCalloc(
dec->info_.canvas_width * NUM_CHANNELS, dec->info_.canvas_height);
if (dec->curr_frame_ == NULL) goto Error;
dec->prev_frame_disposed_ = WebPSafeCalloc(
dec->info_.canvas_width * NUM_CHANNELS, dec->info_.canvas_height);
if (dec->prev_frame_disposed_ == NULL) goto Error;
WebPAnimDecoderReset(dec);
return dec;
Error:
@ -144,9 +141,13 @@ static int IsFullFrame(int width, int height, int canvas_width,
}
// Clear the canvas to transparent.
static void ZeroFillCanvas(uint8_t* buf, uint32_t canvas_width,
uint32_t canvas_height) {
memset(buf, 0, canvas_width * NUM_CHANNELS * canvas_height);
static int ZeroFillCanvas(uint8_t* buf, uint32_t canvas_width,
uint32_t canvas_height) {
const uint64_t size =
(uint64_t)canvas_width * canvas_height * NUM_CHANNELS * sizeof(*buf);
if (size != (size_t)size) return 0;
memset(buf, 0, (size_t)size);
return 1;
}
// Clear given frame rectangle to transparent.
@ -162,10 +163,13 @@ static void ZeroFillFrameRect(uint8_t* buf, int buf_stride, int x_offset,
}
// Copy width * height pixels from 'src' to 'dst'.
static void CopyCanvas(const uint8_t* src, uint8_t* dst,
uint32_t width, uint32_t height) {
static int CopyCanvas(const uint8_t* src, uint8_t* dst,
uint32_t width, uint32_t height) {
const uint64_t size = (uint64_t)width * height * NUM_CHANNELS;
if (size != (size_t)size) return 0;
assert(src != NULL && dst != NULL);
memcpy(dst, src, width * NUM_CHANNELS * height);
memcpy(dst, src, (size_t)size);
return 1;
}
// Returns true if the current frame is a key-frame.
@ -328,9 +332,14 @@ int WebPAnimDecoderGetNext(WebPAnimDecoder* dec,
is_key_frame = IsKeyFrame(&iter, &dec->prev_iter_,
dec->prev_frame_was_keyframe_, width, height);
if (is_key_frame) {
ZeroFillCanvas(dec->curr_frame_, width, height);
if (!ZeroFillCanvas(dec->curr_frame_, width, height)) {
goto Error;
}
} else {
CopyCanvas(dec->prev_frame_disposed_, dec->curr_frame_, width, height);
if (!CopyCanvas(dec->prev_frame_disposed_, dec->curr_frame_,
width, height)) {
goto Error;
}
}
// Decode.