[FFmpeg-devel] [PATCH] avcodec/v4l2_m2m: Fix segmentation fault due to a missing NULL check in v4l2_context.c

[Eslam Samy]

Hi Nicolas,

Sorry for the misunderstanding—this is my first patch submitted to FFmpeg, and I'm still familiarizing myself with the codebase.

The logic behind the change I made is explained here: Ticket #9722. I tried to fix the issue by adding a null check to prevent the segmentation fault when ctx->buffers is accessed before being initialized.

Regarding the coding style, I reviewed the FFmpeg developer documentation, but I couldn't find any explicit rules on this matter. However, I completely understand the importance of adhering to FFmpeg's coding standards, and I would be happy to modify the patch to align with the style you suggest.

Thanks for your feedback, and I look forward to your guidance!

Best regards,
Eslam
    On Tuesday, February 18, 2025 at 01:27:49 PM GMT+2, Nicolas George <george at nsup.org> wrote:  
 
 Thanks for the patch.

Eslam Samy via ffmpeg-devel (HE12025-02-18):
> ---
>  libavcodec/v4l2_context.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/v4l2_context.c b/libavcodec/v4l2_context.c
> index be1df3785b..ea11a689bc 100644
> --- a/libavcodec/v4l2_context.c
> +++ b/libavcodec/v4l2_context.c
> @@ -329,7 +329,7 @@ start:
>          /* if we are trying to get free buffers but none have been queued yet,
>          * or if no buffers have been allocated yet, no need to raise a warning
>          */
> -        if (timeout == 0) {

> +        if ((timeout == 0) && (ctx->buffers != NULL)) {

This does not match ffmpeg's coding style, the extra parentheses and the
!= NULL.

>              if (!ctx->buffers)
>                  return NULL;

Can you explain how this hunk makes sense with your change?

Regards,

-- 
  Nicolas George
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