ffmpeg segfault with musl

ffmpeg segfault with musl

[JS]

Hello

Does anybody have experience/solution with ffmpeg segfaulting with musl? 
The issue happens when mpd tries to play wav file that is decoded by 
ffmpeg. Tested with musl 1.1.17 and 1.1.23 and both old and new ffmpeg 
versions. This does not happen with uClibc on the same hardware.

Re: ffmpeg segfault with musl

[Rich Felker]

On Wed, Sep 18, 2019 at 04:22:06PM +0300, JS wrote:
> Hello
> 
> Does anybody have experience/solution with ffmpeg segfaulting with
> musl? The issue happens when mpd tries to play wav file that is
> decoded by ffmpeg. Tested with musl 1.1.17 and 1.1.23 and both old
> and new ffmpeg versions. This does not happen with uClibc on the
> same hardware.

I'm not aware of any such problem. Are there publicly available files
you can reproduce the crash with? Is mpd necessary or does ffplay
crash too? (easier test case)

Rich

Re: ffmpeg segfault with musl

[A. Wilcox]

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On 18/09/2019 08:50, Rich Felker wrote:
> On Wed, Sep 18, 2019 at 04:22:06PM +0300, JS wrote:
>> Hello
>>
>> Does anybody have experience/solution with ffmpeg segfaulting with
>> musl? The issue happens when mpd tries to play wav file that is
>> decoded by ffmpeg. Tested with musl 1.1.17 and 1.1.23 and both old
>> and new ffmpeg versions. This does not happen with uClibc on the
>> same hardware.
> 
> I'm not aware of any such problem. Are there publicly available files
> you can reproduce the crash with? Is mpd necessary or does ffplay
> crash too? (easier test case)
> 
> Rich


I'll note here if it helps that I've been *incredibly* rough with ffplay
and other ffmpeg consumers (including Firefox, Audacious, VLC) and I've
never experienced an ffmpeg-related segfault on Adélie, ppc64 + x86_64.

By "rough" I mean "files wrongly encoded by misbehaving programs", in
addition to a wide swath of formats.  I wanted to make sure that there
wouldn't be any issues playing back any media.

I've personally tested WAV (16-bit LE and 8-bit LE), AIFF (BE only),
FLAC, AU (Sun only), MP2, MP3, M4A/AAC, Apple Lossless, Opus, WebM
Audio, and CDDA (audio CDs).

I'd be *very* curious to see an example WAV file as well, if they are
unique in any way; this could even be a security-adjacent bug if there
really is a buffer issue in mpd or ffmpeg.

I'm also interested in what the audio stack looks like.  For example, is
this playing back to the ALSA back-end, Pulse, SDL, socket, sndio?  I
*have* seen a bit of trouble out of the ALSA back end at times, and the
SDL output has been no end of trouble.

Best,
--arw


-- 
A. Wilcox (awilfox)
Project Lead, Adélie Linux
https://www.adelielinux.org


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Re: ffmpeg segfault with musl

[Natanael Copa]

On Wed, 18 Sep 2019 16:22:06 +0300
JS <js@direct.lv> wrote:

> Hello
> 
> Does anybody have experience/solution with ffmpeg segfaulting with musl? 
> The issue happens when mpd tries to play wav file that is decoded by 
> ffmpeg. Tested with musl 1.1.17 and 1.1.23 and both old and new ffmpeg 
> versions. This does not happen with uClibc on the same hardware.

FWIW, There is a known issue with mpd and thread stack size:
https://gitlab.alpinelinux.org/alpine/aports/issues/4448

I think i sent the patch upstream years ago, but the response was
something like musl was explicitly not supported because there is no
__MUSL__ define or similar.

I remember this because there are only two projects that I can remember
that has responded that musl is explicitly not supported when sending
patches, and mpd is one of them.

-nc

Re: ffmpeg segfault with musl

[JS]

On Wed, Sep 18, 2019 at 9:32 PM Natanael Copa <ncopa@alpinelinux.org> wrote:
>
> On Wed, 18 Sep 2019 16:22:06 +0300
> JS <js@direct.lv> wrote:
>
> > Hello
> >
> > Does anybody have experience/solution with ffmpeg segfaulting with musl?
> > The issue happens when mpd tries to play wav file that is decoded by
> > ffmpeg. Tested with musl 1.1.17 and 1.1.23 and both old and new ffmpeg
> > versions. This does not happen with uClibc on the same hardware.
>
> FWIW, There is a known issue with mpd and thread stack size:
> https://gitlab.alpinelinux.org/alpine/aports/issues/4448
>
> I think i sent the patch upstream years ago, but the response was
> something like musl was explicitly not supported because there is no
> __MUSL__ define or similar.
>
> I remember this because there are only two projects that I can remember
> that has responded that musl is explicitly not supported when sending
> patches, and mpd is one of them.
>
> -nc

I've increased stack size and could run my custom mpd build on Alpine
VM without segfaults. I'll test it on real hardware later on. Thanks a
lot for your help!