[FFmpeg-devel] [PATCH] avpacket: ABI bump additions

[Lynne]

20 Jul 2021, 00:05 by dev at lynne.ee:

> 8 Jul 2021, 21:20 by andreas.rheinhardt at outlook.com:
>
>> Lynne:
>>
>>> Apr 26, 2021, 03:27 by andreas.rheinhardt at outlook.com:
>>>
>>>> Lynne:
>>>>
>>>>> From 097aed2ac33dda0bb2052d8b0402711ce95079ba Mon Sep 17 00:00:00 2001
>>>>> From: Lynne <dev at lynne.ee>
>>>>> Date: Sat, 23 Jan 2021 19:56:18 +0100
>>>>> Subject: [PATCH] avpacket: ABI bump additions
>>>>>
>>>>> ---
>>>>>  libavcodec/avpacket.c |  5 +++++
>>>>>  libavcodec/packet.h   | 21 +++++++++++++++++++++
>>>>>  2 files changed, 26 insertions(+)
>>>>>
>>>>> diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
>>>>> index e32c467586..03b73b3b53 100644
>>>>> --- a/libavcodec/avpacket.c
>>>>> +++ b/libavcodec/avpacket.c
>>>>> @@ -382,6 +382,10 @@ int av_packet_copy_props(AVPacket *dst, const AVPacket *src)
>>>>>  dst->flags                = src->flags;
>>>>>  dst->stream_index         = src->stream_index;
>>>>>  
>>>>> +    i = av_buffer_replace(&dst->opaque_ref, src->opaque_ref);
>>>>> +    if (i < 0)
>>>>> +        return i;
>>>>>
>>>>
>>>> 1. Don't use i here; add a new variable.
>>>> 2. Up until now, av_packet_ref() and av_packet_copy_props() treat the
>>>> destination packet as uninitialized and make no attempt at unreferencing
>>>> its content; yet you try to reuse opaque_ref. Even worse, you might
>>>> return potentially dangerous packets: If the properties were
>>>> uninitialized and av_packet_copy_props() failed, then the caller were
>>>> not allowed to unreference the packet even when the non-properties were
>>>> set to sane values. The easiest way to fix this is to move setting
>>>> opaque ref to the place after initializing side_data below and either
>>>> set dst->opaque_ref to NULL before av_buffer_replace() or to not use
>>>> av_buffer_replace(). It may also be best to unref it again if copying
>>>> side data fails.
>>>>
>>>>> +
>>>>>  dst->side_data            = NULL;
>>>>>  dst->side_data_elems      = 0;
>>>>>  for (i = 0; i < src->side_data_elems; i++) {
>>>>> @@ -403,6 +407,7 @@ int av_packet_copy_props(AVPacket *dst, const AVPacket *src)
>>>>>  void av_packet_unref(AVPacket *pkt)
>>>>>  {
>>>>>  av_packet_free_side_data(pkt);
>>>>> +    av_buffer_unref(&pkt->opaque_ref);
>>>>>  av_buffer_unref(&pkt->buf);
>>>>>  get_packet_defaults(pkt);
>>>>>  }
>>>>> diff --git a/libavcodec/packet.h b/libavcodec/packet.h
>>>>> index fad8341c12..c29ad18a2b 100644
>>>>> --- a/libavcodec/packet.h
>>>>> +++ b/libavcodec/packet.h
>>>>> @@ -383,6 +383,27 @@ typedef struct AVPacket {
>>>>>  int64_t duration;
>>>>>  
>>>>>  int64_t pos;                            ///< byte position in stream, -1 if unknown
>>>>> +
>>>>> +    /**
>>>>> +     * for some private data of the user
>>>>> +     */
>>>>> +    void *opaque;
>>>>>
>>>>
>>>> The corresponding AVFrame field is copied when copying props.
>>>>
>>>
>>> Fixed both, thanks. Also copied the time_base field and made av_init_packet()
>>> initialize all fields.
>>>
>>
>> Your new version is still not correct: If copying side data fails, the
>> function returns without initializing opaque_ref at all, thereby making
>> it dangerous to unref the packet (which e.g. av_packet_ref() does).
>>
>> - Andreas
>>
>
> Fixed, and made sure to unref it if copying side data fails.
>

Ping.