[FFmpeg-devel] [PATCH v1] libavformat/hls: During operation, the user exits and interrupts, causing pls->segment to be released, resulting in a null pointer crash

[Steven Liu]

> 在 2020年10月17日，13:38，徐慧书 <javashu2012 at gmail.com> 写道：
> 
> Andreas Rheinhardt <andreas.rheinhardt at gmail.com> 于2020年10月16日周五 下午9:32写道：
> 
>> javashu2012 at gmail.com:
>>> From: bevis <javashu2012 at gmail.com>
>>> 
>>> Signed-off-by: bevis <javashu2012 at gmail.com>
>>> ---
>>> libavformat/hls.c | 5 +++--
>>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>> 
>>> diff --git a/libavformat/hls.c b/libavformat/hls.c
>>> index 72e28ab94f..0a522a4595 100644
>>> --- a/libavformat/hls.c
>>> +++ b/libavformat/hls.c
>>> @@ -1979,17 +1979,18 @@ static int hls_read_header(AVFormatContext *s)
>>>         pls->ctx->interrupt_callback = s->interrupt_callback;
>>>         url = av_strdup(pls->segments[0]->url);
>>>         ret = av_probe_input_buffer(&pls->pb, &in_fmt, url, NULL, 0, 0);
>>> -        av_free(url);
>>>         if (ret < 0) {
>>>             /* Free the ctx - it isn't initialized properly at this
>> point,
>>>              * so avformat_close_input shouldn't be called. If
>>>              * avformat_open_input fails below, it frees and zeros the
>>>              * context, so it doesn't need any special treatment like
>> this. */
>>> -            av_log(s, AV_LOG_ERROR, "Error when loading first segment
>> '%s'\n", pls->segments[0]->url);
>>> +            av_log(s, AV_LOG_ERROR, "Error when loading first segment
>> '%s'\n", url);
>>>             avformat_free_context(pls->ctx);
>>>             pls->ctx = NULL;
>>> +            av_free(url);
>>>             goto fail;
>>>         }
>>> +        av_free(url);
>>>         pls->ctx->pb       = &pls->pb;
>>>         pls->ctx->io_open  = nested_io_open;
>>>         pls->ctx->flags   |= s->flags & ~AVFMT_FLAG_CUSTOM_IO;
>>> 
>> The change itself seems fine to me (I wonder why this hasn't been
>> noticed when writing/reviewing b5e39880fb), but your commit message is
>> way too long: The first line should be a short description followed by a
>> more detailed description lateron (in the next lines).
>> 
>> How exactly did you find this?
>> 
>> - Andreas
>> 
> 
> It was found in the crash logs of online users, and it was also simulated
> locally. In China, we have a very large number of users, and the hls
> protocol is widely used, with hundreds of millions of views every day, and
> every small problem becomes more obvious.
maybe more than 1.5 billions right now. :D

> 
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Thanks
Steven