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Date: Mon, 01 Jan 2018 10:03:48 +0100
From: Takashi Iwai <tiwai@...e.de>
To: syzbot <syzbot+6f11c7e2a1b91d466432@...kaller.appspotmail.com>
Cc: <alsa-devel@...a-project.org>, <syzkaller-bugs@...glegroups.com>,
<mingo@...nel.org>, <perex@...ex.cz>,
<linux-kernel@...r.kernel.org>
Subject: Re: WARNING in snd_pcm_hw_param_first
On Sun, 31 Dec 2017 20:58:01 +0100,
syzbot wrote:
>
> Hello,
>
> syzkaller hit the following crash on
> 71ee203389f7cb1c1927eab22b95baa01405791c
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+6f11c7e2a1b91d466432@...kaller.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.
>
> audit: type=1400 audit(1514740357.837:7): avc: denied { map } for
> pid=3502 comm="syzkaller781065" path="/root/syzkaller781065961"
> dev="sda1" ino=16481
> scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
> tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
> WARNING: CPU: 0 PID: 3502 at sound/core/pcm_lib.c:1635
> snd_pcm_hw_param_first+0x289/0x690 sound/core/pcm_lib.c:1635
> Kernel panic - not syncing: panic_on_warn set ...
>
> CPU: 0 PID: 3502 Comm: syzkaller781065 Not tainted 4.15.0-rc5+ #154
> 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+0x194/0x257 lib/dump_stack.c:53
> panic+0x1e4/0x41c kernel/panic.c:183
> __warn+0x1dc/0x200 kernel/panic.c:547
> report_bug+0x211/0x2d0 lib/bug.c:184
> fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
> fixup_bug arch/x86/kernel/traps.c:247 [inline]
> do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
> do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
> invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1079
> RIP: 0010:snd_pcm_hw_param_first+0x289/0x690 sound/core/pcm_lib.c:1635
> RSP: 0018:ffff8801c013f1a0 EFLAGS: 00010293
> RAX: ffff8801c03bc3c0 RBX: ffff8801bff08dc0 RCX: ffffffff841bee19
> RDX: 0000000000000000 RSI: 00000000ffffffea RDI: ffffed0038027e28
> RBP: ffff8801c013f1f0 R08: ffffed0038027d63 R09: ffff8801c013eb10
> R10: 0000000000000001 R11: ffffed0038027d62 R12: 000000000000000d
> R13: 00000000ffffffea R14: 0000000000000005 R15: 0000000000002000
> snd_pcm_hw_param_near.constprop.27+0x78d/0x9a0 sound/core/oss/pcm_oss.c:457
> snd_pcm_oss_change_params+0x17d3/0x3720 sound/core/oss/pcm_oss.c:969
> snd_pcm_oss_make_ready+0xaa/0x130 sound/core/oss/pcm_oss.c:1128
> snd_pcm_oss_sync+0x257/0x830 sound/core/oss/pcm_oss.c:1638
> snd_pcm_oss_release+0x20b/0x280 sound/core/oss/pcm_oss.c:2431
> __fput+0x327/0x7e0 fs/file_table.c:210
> ____fput+0x15/0x20 fs/file_table.c:244
> task_work_run+0x199/0x270 kernel/task_work.c:113
> exit_task_work include/linux/task_work.h:22 [inline]
> do_exit+0x9bb/0x1ad0 kernel/exit.c:865
> do_group_exit+0x149/0x400 kernel/exit.c:968
> SYSC_exit_group kernel/exit.c:979 [inline]
> SyS_exit_group+0x1d/0x20 kernel/exit.c:977
> do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
> do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
> entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
> RIP: 0023:0xf7f4ec79
> RSP: 002b:00000000ffc2c18c EFLAGS: 00000292 ORIG_RAX: 00000000000000fc
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000080f0298
> RDX: 0000000000000000 RSI: 00000000080d9b78 RDI: 00000000080f02a0
> RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> Dumping ftrace buffer:
> (ftrace buffer empty)
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
This must be a superfluous WARN_ON() call invoked by snd_BUG_ON()
check that can be safely ignored. A quick fix patch is below.
thanks,
Takashi
-- 8< --
From: Takashi Iwai <tiwai@...e.de>
Subject: [PATCH] ALSA: pcm: Remove superfluous warning
syzkaller triggered kernel warnings through PCM OSS emulation at
closing a stream:
WARNING: CPU: 0 PID: 3502 at sound/core/pcm_lib.c:1635
snd_pcm_hw_param_first+0x289/0x690 sound/core/pcm_lib.c:1635
Call Trace:
....
snd_pcm_hw_param_near.constprop.27+0x78d/0x9a0 sound/core/oss/pcm_oss.c:457
snd_pcm_oss_change_params+0x17d3/0x3720 sound/core/oss/pcm_oss.c:969
snd_pcm_oss_make_ready+0xaa/0x130 sound/core/oss/pcm_oss.c:1128
snd_pcm_oss_sync+0x257/0x830 sound/core/oss/pcm_oss.c:1638
snd_pcm_oss_release+0x20b/0x280 sound/core/oss/pcm_oss.c:2431
__fput+0x327/0x7e0 fs/file_table.c:210
....
It's a spurious snd_BUG_ON() that invokes WARN_ON(). An error
returned from snd_pcm_hw_refine() shouldn't be treated as an
exception, but dealt as a normal error path.
There are a couple of other places using snd_BUG_ON() unnecessarily,
and this patch removes these spurious snd_BUG_ON() calls.
Reported-by: syzbot+6f11c7e2a1b91d466432@...kaller.appspotmail.com
Cc: <stable@...r.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
sound/core/oss/pcm_oss.c | 1 -
sound/core/pcm_lib.c | 4 ++--
2 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index e49f448ee04f..ceaa51f76591 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -455,7 +455,6 @@ static int snd_pcm_hw_param_near(struct snd_pcm_substream *pcm,
v = snd_pcm_hw_param_last(pcm, params, var, dir);
else
v = snd_pcm_hw_param_first(pcm, params, var, dir);
- snd_BUG_ON(v < 0);
return v;
}
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 10e7ef7a8804..db7894bb028c 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -1632,7 +1632,7 @@ int snd_pcm_hw_param_first(struct snd_pcm_substream *pcm,
return changed;
if (params->rmask) {
int err = snd_pcm_hw_refine(pcm, params);
- if (snd_BUG_ON(err < 0))
+ if (err < 0)
return err;
}
return snd_pcm_hw_param_value(params, var, dir);
@@ -1678,7 +1678,7 @@ int snd_pcm_hw_param_last(struct snd_pcm_substream *pcm,
return changed;
if (params->rmask) {
int err = snd_pcm_hw_refine(pcm, params);
- if (snd_BUG_ON(err < 0))
+ if (err < 0)
return err;
}
return snd_pcm_hw_param_value(params, var, dir);
--
2.15.1
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