[FFmpeg-devel] Re: [PATCH] avformat/whip: Fix rtp_ctx->streams access (PR #20805)

[Jack Lau via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

> On Nov 10, 2025, at 08:24, Michael Niedermayer via ffmpeg-devel <ffmpeg-devel@ffmpeg.org> wrote:
> 
> Hi Kieran
> 
> On Sat, Nov 01, 2025 at 02:37:45AM +0000, Kieran Kunhya via ffmpeg-devel wrote:
>> On Fri, 31 Oct 2025, 17:06 michaelni via ffmpeg-devel, <
>> ffmpeg-devel@ffmpeg.org> wrote:
>> 
>>> PR #20805 opened by michaelni
>>> URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20805
>>> Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20805.patch
>>> 
>>> Fixes: out of array access
>>> No testcase
>>> 
>>> Found-by: Joshua Rogers <joshua@joshua.hu> with ZeroPath
>>> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
>>> 
>>> 
>>>> From e01eb935a6b919d0bc4361e30a0ab00ff01783af Mon Sep 17 00:00:00 2001
>>> From: Michael Niedermayer <michael@niedermayer.cc>
>>> Date: Fri, 31 Oct 2025 18:00:11 +0100
>>> Subject: [PATCH] avformat/whip: Fix rtp_ctx->streams access
>>> 
>>> Fixes: out of array access
>>> No testcase
>>> 
>>> Found-by: Joshua Rogers <joshua@joshua.hu> with ZeroPath
>>> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
>>> ---
>>> libavformat/whip.c | 4 ++--
>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>> 
>>> diff --git a/libavformat/whip.c b/libavformat/whip.c
>>> index a11fffb9c6..6a9b208f69 100644
>>> --- a/libavformat/whip.c
>>> +++ b/libavformat/whip.c
>>> @@ -1592,8 +1592,8 @@ static int create_rtp_muxer(AVFormatContext *s)
>>>          * therefore, we deactivate the extradata detection for the RTP
>>> muxer.
>>>          */
>>>         if (s->streams[i]->codecpar->codec_id == AV_CODEC_ID_H264) {
>>> -            av_freep(&rtp_ctx->streams[i]->codecpar->extradata);
>>> -            rtp_ctx->streams[i]->codecpar->extradata_size = 0;
>>> +            av_freep(&rtp_ctx->streams[0]->codecpar->extradata);
>>> +            rtp_ctx->streams[0]->codecpar->extradata_size = 0;
>>>         }
>>> 
>>>         buffer = av_malloc(buffer_size);
>>> 
>> 
>> Both the original code and the fix are weird.
> 
> I agree, a better fix is welcome,

Hi

This PR https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20931 try to fix it 
Thanks for pointing this issue out

Regards,
Jack

> but until then, this fix was approved by 3 people
> including the author of teh whip code. And it fixes the out of array access
> fixing the weirdness is out of the scope of this fix.
> 
> thx
> 
> [...]
> -- 
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> 
> Its not that you shouldnt use gotos but rather that you should write
> readable code and code with gotos often but not always is less readable
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