On Tue, 27 Mar 2018 14:27:30 +0200,
Dan Carpenter wrote:
>
> Hello Takashi Iwai,
>
> The patch 40cab6e88cb0: "ALSA: pcm: Return -EBUSY for OSS ioctls
> changing busy streams" from Mar 23, 2018, leads to the following
> static checker warning:
>
> sound/core/oss/pcm_oss.c:1741 snd_pcm_oss_set_rate()
> warn: inconsistent returns 'mutex:&runtime->oss.params_lock'.
> Locked on: line 1734
> Unlocked on: line 1732
> line 1741
>
> sound/core/oss/pcm_oss.c
> 1717 static int snd_pcm_oss_set_rate(struct snd_pcm_oss_file *pcm_oss_file, int rate)
> 1718 {
> 1719 int idx;
> 1720
> 1721 for (idx = 1; idx >= 0; --idx) {
> 1722 struct snd_pcm_substream *substream = pcm_oss_file->streams[idx];
> 1723 struct snd_pcm_runtime *runtime;
> 1724 if (substream == NULL)
> 1725 continue;
> 1726 runtime = substream->runtime;
> 1727 if (rate < 1000)
> 1728 rate = 1000;
> 1729 else if (rate > 192000)
> 1730 rate = 192000;
> 1731 if (mutex_lock_interruptible(&runtime->oss.params_lock))
> 1732 return -ERESTARTSYS;
> 1733 if (atomic_read(&runtime->oss.rw_ref))
> 1734 return -EBUSY;
> ^^^^^^^^^^^^^
> Unlock before returning?
My bad, it has to be checked before mutex_lock.
There is one another place doing the same mistake.
The fix patch is below.
thanks,
Takashi
-- 8< --
From: Takashi Iwai <tiwai@xxxxxxx>
Subject: [PATCH] ALSA: pcm: Fix mutex unbalance in OSS emulation ioctls
The previous fix 40cab6e88cb0 ("ALSA: pcm: Return -EBUSY for OSS
ioctls changing busy streams") introduced some mutex unbalance, the
check of runtime->oss.rw_ref was inserted in a wrong place after the
mutex lock although it should have been done before the mutex lock.
Fix those spots.
Fixes: 40cab6e88cb0 ("ALSA: pcm: Return -EBUSY for OSS ioctls changing busy streams")
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
sound/core/oss/pcm_oss.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index a9082f219561..b01611d1a5f0 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1728,10 +1728,10 @@ static int snd_pcm_oss_set_rate(struct snd_pcm_oss_file *pcm_oss_file, int rate)
rate = 1000;
else if (rate > 192000)
rate = 192000;
- if (mutex_lock_interruptible(&runtime->oss.params_lock))
- return -ERESTARTSYS;
if (atomic_read(&runtime->oss.rw_ref))
return -EBUSY;
+ if (mutex_lock_interruptible(&runtime->oss.params_lock))
+ return -ERESTARTSYS;
if (runtime->oss.rate != rate) {
runtime->oss.params = 1;
runtime->oss.rate = rate;
@@ -1764,10 +1764,10 @@ static int snd_pcm_oss_set_channels(struct snd_pcm_oss_file *pcm_oss_file, unsig
if (substream == NULL)
continue;
runtime = substream->runtime;
- if (mutex_lock_interruptible(&runtime->oss.params_lock))
- return -ERESTARTSYS;
if (atomic_read(&runtime->oss.rw_ref))
return -EBUSY;
+ if (mutex_lock_interruptible(&runtime->oss.params_lock))
+ return -ERESTARTSYS;
if (runtime->oss.channels != channels) {
runtime->oss.params = 1;
runtime->oss.channels = channels;
--
2.16.2
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