Re: [FFmpeg-devel] [PATCH] avutil/hwcontext: check the null pointer input value before use it

[James Almer <jamrial@gmail.com>]

On 2/10/2022 9:20 AM, Steven Liu wrote:
> because the src, src->hw_frames_ctx and src->hw_frames_ctx->data can be
> set to null when the user calling av_hwframe_transfer_data, this will
> get crash if they are null.

src can not be NULL. The doxy doesn't allow it.

And if transfer_data_alloc() is called, it's because dst is "clean", and 
src must then have a hw_frames_ctx (The doxy explicitly states "At least 
one of dst/src must have an AVHWFramesContext attached").

> 
> Signed-off-by: Steven Liu <lq@chinaffmpeg.org>
> ---
>   libavutil/hwcontext.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/libavutil/hwcontext.c b/libavutil/hwcontext.c
> index 31c7840dba..b42a3a6d4d 100644
> --- a/libavutil/hwcontext.c
> +++ b/libavutil/hwcontext.c
> @@ -396,10 +396,13 @@ int av_hwframe_transfer_get_formats(AVBufferRef *hwframe_ref,
>   
>   static int transfer_data_alloc(AVFrame *dst, const AVFrame *src, int flags)
>   {
> -    AVHWFramesContext *ctx = (AVHWFramesContext*)src->hw_frames_ctx->data;
> +    AVHWFramesContext *ctx = NULL;
>       AVFrame *frame_tmp;
>       int ret = 0;
>   
> +    if (!src || !src->hw_frames_ctx || !src->hw_frames_ctx->data)
> +        return AVERROR(EINVAL);
> +    ctx = (AVHWFramesContext*)src->hw_frames_ctx->data;
>       frame_tmp = av_frame_alloc();
>       if (!frame_tmp)
>           return AVERROR(ENOMEM);
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