[FFmpeg-devel] [PATCH] avcodec/mpegpicture: guard "stride changed" failures against unknown uvlinesize

[Michael Niedermayer]

On Tue, Apr 10, 2018 at 10:20:07AM -0700, Aman Gupta wrote:
> From: Aman Gupta <aman at tmm1.net>
> 
> Before adding uvlinesize check, I was seeing failures decoding
> some samples (shown with extra logging added):
> 
> [mpeg2video @ 0x7fa193818c00] get_buffer() failed (stride changed: linesize=1280/1280 uvlinesize=0/640)
> [mpeg2video @ 0x7fa193818c00] get_buffer() failed (stride changed: linesize=1280/1280 uvlinesize=0/640)
> ---
>  libavcodec/mpegpicture.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/libavcodec/mpegpicture.c b/libavcodec/mpegpicture.c
> index 2be670cdbc..80898c161c 100644
> --- a/libavcodec/mpegpicture.c
> +++ b/libavcodec/mpegpicture.c
> @@ -148,10 +148,13 @@ static int alloc_frame_buffer(AVCodecContext *avctx,  Picture *pic,
>          }
>      }
>  
> -    if (linesize && (linesize   != pic->f->linesize[0] ||
> -                     uvlinesize != pic->f->linesize[1])) {
> +    if (linesize && uvlinesize &&
> +        (linesize   != pic->f->linesize[0] ||
> +         uvlinesize != pic->f->linesize[1])) {

without checking if this can be reached with grayscale.
If it can then uvlinesize may be 0 in which case this change would be
wrong

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Observe your enemies, for they first find out your faults. -- Antisthenes
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