[alsa-devel] WARNING in snd_pcm_hw_params
Hello,
syzbot hit the following crash on upstream commit 3c8ba0d61d04ced9f8d9ff93977995a9e4e96e91 (Sat Mar 31 01:52:36 2018 +0000) kernel.h: Retain constant expression output for max()/min() syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=803e0047ac3a3096bb4f
So far this crash happened 6 times on upstream. C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5886672973594624 syzkaller reproducer: https://syzkaller.appspot.com/x/repro.syz?id=4913841943085056 Raw console output: https://syzkaller.appspot.com/x/log.txt?id=6314122077536256 Kernel config: https://syzkaller.appspot.com/x/.config?id=-1647968177339044852 compiler: gcc (GCC) 8.0.1 20180301 (experimental)
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+803e0047ac3a3096bb4f@syzkaller.appspotmail.com It will help syzbot understand when the bug is fixed. See footer for details. If you forward the report, please keep this part and the footer.
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441939 RDX: 0000000000000001 RSI: 0000000020000180 RDI: 0000000000000003 RBP: 00007ffe8c3569b0 R08: 0000000000000002 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005 R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000 WARNING: CPU: 0 PID: 4468 at sound/core/pcm_native.c:620 snd_pcm_hw_params_choose sound/core/pcm_native.c:620 [inline] WARNING: CPU: 0 PID: 4468 at sound/core/pcm_native.c:620 snd_pcm_hw_params+0x65a/0x1e20 sound/core/pcm_native.c:672 Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 4468 Comm: syzkaller371267 Not tainted 4.16.0+ #2 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x1b9/0x29f lib/dump_stack.c:53 panic+0x22f/0x4de kernel/panic.c:183 __warn.cold.8+0x163/0x1a3 kernel/panic.c:547 report_bug+0x252/0x2d0 lib/bug.c:186 fixup_bug arch/x86/kernel/traps.c:178 [inline] do_error_trap+0x1bc/0x470 arch/x86/kernel/traps.c:296 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:991 RIP: 0010:snd_pcm_hw_params_choose sound/core/pcm_native.c:620 [inline] RIP: 0010:snd_pcm_hw_params+0x65a/0x1e20 sound/core/pcm_native.c:672 RSP: 0018:ffff8801ac66f498 EFLAGS: 00010293 RAX: ffff8801acb86580 RBX: 00000000fffffff4 RCX: ffffffff859d7220 RDX: 0000000000000000 RSI: ffffffff859d752a RDI: 0000000000000005 RBP: ffff8801ac66f6e8 R08: ffff8801acb86580 R09: ffffed003b6046c2 R10: ffffed003b6046c2 R11: ffff8801db023613 R12: ffffffff8826309c R13: ffff8801ceab6940 R14: ffff8801d9509200 R15: dffffc0000000000 snd_pcm_kernel_ioctl+0x6c/0x240 sound/core/pcm_native.c:2999 snd_pcm_oss_change_params_locked+0x1be8/0x3ce0 sound/core/oss/pcm_oss.c:993 snd_pcm_oss_make_ready_locked+0xbc/0x130 sound/core/oss/pcm_oss.c:1182 snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1396 [inline] snd_pcm_oss_write+0x516/0xa20 sound/core/oss/pcm_oss.c:2774 __vfs_write+0x10b/0x880 fs/read_write.c:485 vfs_write+0x1f8/0x560 fs/read_write.c:549 ksys_write+0xf9/0x250 fs/read_write.c:598 SYSC_write fs/read_write.c:610 [inline] SyS_write+0x24/0x30 fs/read_write.c:607 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x441939 RSP: 002b:00007ffe8c3568e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441939 RDX: 0000000000000001 RSI: 0000000020000180 RDI: 0000000000000003 RBP: 00007ffe8c3569b0 R08: 0000000000000002 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005 R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000 Dumping ftrace buffer: (ftrace buffer empty) Kernel Offset: disabled Rebooting in 86400 seconds..
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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...
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@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+803e0047ac3a3096bb4f@syzkaller.appspotmail.com Signed-off-by: Takashi Iwai tiwai@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;
On Mon, Apr 9, 2018 at 5:18 PM, Takashi Iwai tiwai@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?
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@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+803e0047ac3a3096bb4f@syzkaller.appspotmail.com Signed-off-by: Takashi Iwai tiwai@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
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On Mon, 09 Apr 2018 17:25:15 +0200, Dmitry Vyukov wrote:
On Mon, Apr 9, 2018 at 5:18 PM, Takashi Iwai tiwai@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 tiwai@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+803e0047ac3a3096bb4f@syzkaller.appspotmail.com Signed-off-by: Takashi Iwai tiwai@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
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On Mon, 09 Apr 2018 17:33:45 +0200, Takashi Iwai wrote:
On Mon, 09 Apr 2018 17:25:15 +0200, Dmitry Vyukov wrote:
On Mon, Apr 9, 2018 at 5:18 PM, Takashi Iwai tiwai@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.
... and below is the revised patch. I'll queue for 4.17-rc1 merge.
Takashi
-- 8< -- From: Takashi Iwai tiwai@suse.de Subject: [PATCH] ALSA: pcm: Remove WARN_ON() at snd_pcm_hw_params() error
snd_pcm_hw_params() (more exactly snd_pcm_hw_params_choose()) contains a check of the return error from snd_pcm_hw_param_first() and _last() with snd_BUG_ON() -- i.e. it may trigger WARN_ON() depending on the kconfig.
This was a valid check in the past, as these functions shouldn't return any error if the parameters have been already refined via snd_pcm_hw_refine() beforehand. However, the recent rewrite introduced a kmalloc() in snd_pcm_hw_refine() for removing VLA, and this brought a possibility to trigger an error. As a result, syzbot caught lots of superfluous kernel WARN_ON() and paniced via fault injection.
As the WARN_ON() is no longer valid with the introduction of kmalloc(), let's drop snd_BUG_ON() check, in order to make the world peaceful place again.
Reported-by: syzbot+803e0047ac3a3096bb4f@syzkaller.appspotmail.com Fixes: 5730f9f744cf ("ALSA: pcm: Remove VLA usage") Signed-off-by: Takashi Iwai tiwai@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;
participants (3)
-
Dmitry Vyukov -
syzbot -
Takashi Iwai