On Mon, 09 Apr 2018 17:25:15 +0200, Dmitry Vyukov wrote: > > On Mon, Apr 9, 2018 at 5:18 PM, Takashi Iwai <ti...@suse.de> 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?
Yes, it does. So it's the kmalloc error from snd_pcm_hw_refine(). I overlooked this, as this kmalloc is relatively new, and that possibility wasn't considered in the WARN_ON() in question. I'll rephrase the changelog text. Thanks! Takashi > > > 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 <ti...@suse.de> > > 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+803e0047ac3a3096b...@syzkaller.appspotmail.com > > Signed-off-by: Takashi Iwai <ti...@suse.de> > > --- > > 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+unsubscr...@googlegroups.com. > > 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. >