On Mon, Apr 9, 2018 at 5:18 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: > On Fri, 06 Apr 2018 02:02:02 +0200, > syzbot wrote: >> >> WARNING: CPU: 0 PID: 4468 at sound/core/pcm_native.c:620 >> snd_pcm_hw_params_choose sound/core/pcm_native.c:620 [inline] > > This is a WARN_ON() to catch the inconsistent hw_params call. > This shouldn't happen in theory, but the reality looks weirder. > > The necessary "fix" is just to get rid of snd_BUG_ON(), but still > wonder which condition it hits. If it's an empty parameter, the > previous snd_pcm_hw_refine() should have caught and returned the error > beforehand... Hi Takashi, The reproducer for this is trivially simple: https://syzkaller.appspot.com/x/repro.syz?id=4913841943085056 (and I guess perf_event_open is red herring). But the really important part there is probably this: Fault:true FaultCall:2 FaultNth:18 And you can see where it actually happened in the raw console log: Raw console output: https://syzkaller.appspot.com/x/log.txt?id=6314122077536256 Does it explain things? > In anyway this can't be a real crash, let's remove the warning to stop > the chorus of syzbot birds. > > > thanks, > > Takashi > > -- 8< -- > From: Takashi Iwai <tiwai@xxxxxxx> > Subject: [PATCH] ALSA: pcm: Remove WARN_ON() at snd_pcm_hw_params() error > > snd_pcm_hw_params() may hit WARN_ON() when an inconsistent parameter > set is passed. Although this should have been caught by the former > snd_pcm_hw_refine() and returned the error, syzkaller succeeded to > pass through and hit the WARN_ON(), which in turn made it panic > unnecessarily. > > For reducing this kind of noise, let's drop snd_BUG_ON() check. > > Reported-by: syzbot+803e0047ac3a3096bb4f@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> > --- > sound/core/pcm_native.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c > index b84554893fab..35ffccea94c3 100644 > --- a/sound/core/pcm_native.c > +++ b/sound/core/pcm_native.c > @@ -617,7 +617,7 @@ static int snd_pcm_hw_params_choose(struct snd_pcm_substream *pcm, > changed = snd_pcm_hw_param_first(pcm, params, *v, NULL); > else > changed = snd_pcm_hw_param_last(pcm, params, *v, NULL); > - if (snd_BUG_ON(changed < 0)) > + if (changed < 0) > return changed; > if (changed == 0) > continue; > -- > 2.16.3 > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/s5hbmesflxu.wl-tiwai%40suse.de. > For more options, visit https://groups.google.com/d/optout. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
