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d3d11decoder: Fix potential use after free

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A DPB buffer held by codec picture object may not be writable
at the moment, then gst_buffer_make_writable() will unref passed buffer.

Specifically, the use after free or double free can happen if:
* Crop meta of buffer copy is required because of non-zero
  top-left crop position
* zero-copy is possible with crop meta
* A picture was duplicated, interlaced h264 stream for example

Interlaced h264 stream with non-zero top-left crop position
is not very common but it's possible configuration in theory.

Thus gst_buffer_make_writable() should be called with
GstVideoCodecFrame.output_buffer directly.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6706>
This commit is contained in:
Seungha Yang 2024-04-21 22:07:36 +09:00 committed by GStreamer Marge Bot
parent 6d228c420c
commit b9e51facdd
1 changed files with 15 additions and 15 deletions
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30
subprojects/gst-plugins-bad/sys/d3d11/gstd3d11decoder.cpp
View file

@ -1551,6 +1551,7 @@ gst_d3d11_decoder_output_picture (GstD3D11Decoder * decoder,
{
GstFlowReturn ret = GST_FLOW_OK;
GstBuffer *view_buffer;
bool attach_crop_meta = false;
if (picture->discont_state) {
g_clear_pointer (&decoder->input_state, gst_video_codec_state_unref);
@ -1593,21 +1594,8 @@ gst_d3d11_decoder_output_picture (GstD3D11Decoder * decoder,
mem = gst_buffer_peek_memory (view_buffer, 0);
GST_MINI_OBJECT_FLAG_SET (mem, GST_D3D11_MEMORY_TRANSFER_NEED_DOWNLOAD);
if (decoder->need_crop) {
GstVideoCropMeta *crop_meta;
view_buffer = gst_buffer_make_writable (view_buffer);
crop_meta = gst_buffer_get_video_crop_meta (view_buffer);
if (!crop_meta)
crop_meta = gst_buffer_add_video_crop_meta (view_buffer);
crop_meta->x = decoder->offset_x;
crop_meta->y = decoder->offset_y;
crop_meta->width = decoder->info.width;
crop_meta->height = decoder->info.height;
GST_TRACE_OBJECT (decoder, "Attatching crop meta");
}
if (decoder->need_crop)
attach_crop_meta = true;
frame->output_buffer = gst_buffer_ref (view_buffer);
} else {
@ -1628,6 +1616,18 @@ gst_d3d11_decoder_output_picture (GstD3D11Decoder * decoder,
GST_BUFFER_FLAG_SET (frame->output_buffer, buffer_flags);
gst_codec_picture_unref (picture);
if (attach_crop_meta) {
frame->output_buffer = gst_buffer_make_writable (frame->output_buffer);
auto crop_meta = gst_buffer_add_video_crop_meta (frame->output_buffer);
crop_meta->x = decoder->offset_x;
crop_meta->y = decoder->offset_y;
crop_meta->width = decoder->info.width;
crop_meta->height = decoder->info.height;
GST_TRACE_OBJECT (decoder, "Attatching crop meta");
}
return gst_video_decoder_finish_frame (videodec, frame);
error: