[FFmpeg-devel] n4.4 release bug (?) on ffmpeg.c av_fifo_generic_read

[James Almer]

On 4/17/2021 10:16 PM, Đông Nguyễn wrote:
> Hi,
> 
> Not sure this is the correct place to post this, but I've noticed some
> recent changes (n.4.4) on ffmpeg.c which seems suspicious to me.
> 
> https://github.com/FFmpeg/FFmpeg/blob/n4.4/fftools/ffmpeg.c#L532-L535

This one is in 4.3 too. Not sure why you think it was changed for 4.4.

> https://github.com/FFmpeg/FFmpeg/blob/n4.4/fftools/ffmpeg.c#L614-L616
> 
> IIRC, before these changes, av_fifo_generic_read operates on whole struct
> of AVFrame and AVPacket, not sole pointer (which has only 8 bytes on 64bit
> machine)
> 
> After that, calling "free" on those pointers potentially causes malloc heap
> crashes.
> 
> Please correct me if I'm wrong. Thanks

Both FIFOs effectively store pointers to dynamically allocated structs, 
and not entire structs. So reading sizeof(void*) worth of bytes is intended.

> 
> Dong Nguyen
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