[alsa-devel] [PATCH] pcm: route: Don't handle no matching chmap as a serious error

[Takashi Iwai]

At Wed, 19 Mar 2014 13:10:55 +0100,
David Henningsson wrote:
> 
> On 03/19/2014 10:57 AM, Takashi Iwai wrote:
> > At Tue, 18 Mar 2014 23:13:02 +0100,
> > David Henningsson wrote:
> >>
> >> On 03/18/2014 05:34 PM, Takashi Iwai wrote:
> >>> At Tue, 18 Mar 2014 17:19:29 +0100,
> >>> David Henningsson wrote:
> >>>>
> >>>> On 03/18/2014 03:27 PM, Takashi Iwai wrote:
> >>>>> When find_matching_chmap() returns an error for the non-matching
> >>>>> chmap, the caller, snd_pcm_route_open(), also returns an error
> >>>>> although it shouldn't be handled as the fatal error.  This results in
> >>>>> the probe error with PulseAudio and it gives no real output in the
> >>>>> end.
> >>>>
> >>>> Hmm, could you give a more specific example? In case the driver does not
> >>>> support channel maps at all, that case is handled in the beginning of
> >>>> the function.
> >>>
> >>> Well, the problem is that PulseAudio doesn't work at all with the
> >>> current alsa-lib git prior to the commit in some cases.  That is, the
> >>> commit brought some incompatibility.
> >>
> >> Hmm, then the error should be somewhere in determine_chmap instead.
> >> tt_chmap should be NULL (i e, find_matching_chmap is never called) for
> >> using the standard number syntax instead of the new chmap syntax.
> >>
> >> What about the patch attached instead (untested) ?
> >>
> >>>> So this only happens if the driver supports channel maps, but only
> >>>> non-compatible with the requested map. In which case I believe it's
> >>>> correct that the probing should fail...?
> >>>
> >>> Could you check whether PA 5.0 works as is with alsa-lib git (before
> >>> the last fix)?  It could be seen on some desktop machines.
> >>
> >> Let me know if the attached patch works for you. In case it does not I
> >> will do this testing later.
> > 
> > It seems working, but it revealed another bug, too.  I fixed it in git
> > tree, and reverted my last patch along with it.
> 
> I don't think the patch "route: Fix invalid pointer access" is necessary
> because determine_chmap is always called before any usage of tt_chmap,
> and the function always assigns a value to tt_chmap.

It crashed in snd_pcm_route_close() before my fix.  It called free()
with an uninitialized pointer.


Takashi