Re: [FFmpeg-devel] [PATCH 1/2] avcodec/decode: Fix member access within null pointer

[James Almer <jamrial@gmail.com>]

On 7/8/2024 12:58 PM, Andreas Rheinhardt wrote:
> This "works" because the public AVCodecHWConfig is at the beginning of
> AVCodecHWConfigInternal.
> 
> Fixes libavcodec/decode.c:1035:61: runtime error: member access within
> null pointer of type 'const struct AVCodecHWConfigInternal'.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> ---
>   libavcodec/decode.c | 7 +++----
>   1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
> index 791940648d..cdb682cf69 100644
> --- a/libavcodec/decode.c
> +++ b/libavcodec/decode.c
> @@ -1023,6 +1023,7 @@ enum AVPixelFormat avcodec_default_get_format(struct AVCodecContext *avctx,
>                                                 const enum AVPixelFormat *fmt)
>   {
>       const AVPixFmtDescriptor *desc;
> +    const FFCodec *const codec = ffcodec(avctx->codec);
>       const AVCodecHWConfig *config;
>       int i, n;
>   
> @@ -1031,10 +1032,8 @@ enum AVPixelFormat avcodec_default_get_format(struct AVCodecContext *avctx,
>       if (avctx->hw_device_ctx && ffcodec(avctx->codec)->hw_configs) {
>           AVHWDeviceContext *device_ctx =
>               (AVHWDeviceContext*)avctx->hw_device_ctx->data;
> -        for (i = 0;; i++) {
> -            config = &ffcodec(avctx->codec)->hw_configs[i]->public;
> -            if (!config)
> -                break;
> +        for (size_t i = 0; codec->hw_configs[i]; i++) {

nit: Change both i and n to size_t above instead of shadowing i here. Or 
just don't change the type at all.

> +            config = &codec->hw_configs[i]->public;
>               if (!(config->methods &
>                     AV_CODEC_HW_CONFIG_METHOD_HW_DEVICE_CTX))
>                   continue;
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