Re: [FFmpeg-devel] [PATCH] avformat/asfdec: fix crash caused by free wlid pointers

[XiaoYang <yshaw1999@163.com>]

At 2022-01-11 17:29:35, "Andreas Rheinhardt" <andreas.rheinhardt@outlook.com> wrote:
>Yang Xiao:
>> From: Yang Xiao <yshaw99@outlook.com>
>> 
>> This commit fixed a crash when seeking wma frames, asf decoder will try to demux in function asf_read_pts().
>> Pointer member side_data of AVPacket that allocated by stack may be wild pointer.
>> Prevent releasing wild pointers in AVPacket when some functions try to call av_packet_unref, example av_read_frame().
>> ---
>>  libavformat/asfdec_f.c | 2 +-
>>  libavformat/mpc.c      | 2 +-
>>  2 files changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/libavformat/asfdec_f.c b/libavformat/asfdec_f.c
>> index a8f36ed286..bae0ecfc7c 100644
>> --- a/libavformat/asfdec_f.c
>> +++ b/libavformat/asfdec_f.c
>> @@ -1433,7 +1433,7 @@ static int64_t asf_read_pts(AVFormatContext *s, int stream_index,
>>  {
>>      FFFormatContext *const si = ffformatcontext(s);
>>      ASFContext *asf     = s->priv_data;
>> -    AVPacket pkt1, *pkt = &pkt1;
>> +    AVPacket pkt1 = {0}, *pkt = &pkt1;
>>      ASFStream *asf_st;
>>      int64_t pts;
>>      int64_t pos = *ppos;
>> diff --git a/libavformat/mpc.c b/libavformat/mpc.c
>> index b5b2bab33c..ad0d693152 100644
>> --- a/libavformat/mpc.c
>> +++ b/libavformat/mpc.c
>> @@ -189,7 +189,7 @@ static int mpc_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp
>>      AVStream *st = s->streams[stream_index];
>>      FFStream *const sti = ffstream(st);
>>      MPCContext *c = s->priv_data;
>> -    AVPacket pkt1, *pkt = &pkt1;
>> +    AVPacket pkt1 = {0}, *pkt = &pkt1;
>>      int ret;
>>      int index = av_index_search_timestamp(st, FFMAX(timestamp - DELAY_FRAMES, 0), flags);
>>      uint32_t lastframe;
>> 
>
>Do you have FF_API_INIT_PACKET set to 0 (it should still be set to 1)?
>Because av_read_frame() is supposed to (and documented to) treat the
>packet it is given as uninitialized.

>
>- Andreas



Thanks for your comment!
But I have a question,  av_init_packet() has been markedattribute_deprecated, If av_init_packet() is deprecated completely in the future, how to ensure ff_read_packet() safely (support to input a uninitialized packet) ? AVPacket->side_data will not be safely initialized with only av_packet_unref().


And as a user of the FFmpeg API, I want to disable some of the functions marked attribute_deprecated early, because upgrading FFmpeg has a large impact. 
Do I have other ways to achieve this goal?


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