[PATCH 3.16 059/366] ALSA: pcm: Fix mutex unbalance in OSS emulation ioctls

Ben Hutchings
2018-10-14T23:19:50Z

From: Takashi Iwai <tiwai@suse.de>

commit f6d297df4dd47ef949540e4a201230d0c5308325 upstream.

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.

This patch fixes the inconsistency by rewriting with the helper
functions to lock/unlock parameters with the stream check.

Fixes: 40cab6e88cb0 ("ALSA: pcm: Return -EBUSY for OSS ioctls changing busy streams")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
sound/core/oss/pcm_oss.c | 67 +++++++++++++++++++++++++---------------
1 file changed, 42 insertions(+), 25 deletions(-)

--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -833,6 +833,23 @@ static int choose_rate(struct snd_pcm_su
return snd_pcm_hw_param_near(substream, params, SNDRV_PCM_HW_PARAM_RATE, best_rate, NULL);
}

+/* parameter locking: returns immediately if tried during streaming */
+static int lock_params(struct snd_pcm_runtime *runtime)
+{
+ if (mutex_lock_interruptible(&runtime->oss.params_lock))
+ return -ERESTARTSYS;
+ if (atomic_read(&runtime->oss.rw_ref)) {
+ mutex_unlock(&runtime->oss.params_lock);
+ return -EBUSY;
+ }
+ return 0;
+}
+
+static void unlock_params(struct snd_pcm_runtime *runtime)
+{
+ mutex_unlock(&runtime->oss.params_lock);
+}
+
/* call with params_lock held */
static int snd_pcm_oss_change_params_locked(struct snd_pcm_substream *substream)
{
@@ -1774,6 +1791,8 @@ static int snd_pcm_oss_set_rate(struct s
for (idx = 1; idx >= 0; --idx) {
struct snd_pcm_substream *substream = pcm_oss_file->streams[idx];
struct snd_pcm_runtime *runtime;
+ int err;
+
if (substream == NULL)
continue;
runtime = substream->runtime;
@@ -1781,15 +1800,14 @@ static int snd_pcm_oss_set_rate(struct s
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;
+ err = lock_params(runtime);
+ if (err < 0)
+ return err;
if (runtime->oss.rate != rate) {
runtime->oss.params = 1;
runtime->oss.rate = rate;
}
- mutex_unlock(&runtime->oss.params_lock);
+ unlock_params(runtime);
}
return snd_pcm_oss_get_rate(pcm_oss_file);
}
@@ -1814,18 +1832,19 @@ static int snd_pcm_oss_set_channels(stru
for (idx = 1; idx >= 0; --idx) {
struct snd_pcm_substream *substream = pcm_oss_file->streams[idx];
struct snd_pcm_runtime *runtime;
+ int err;
+
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;
+ err = lock_params(runtime);
+ if (err < 0)
+ return err;
if (runtime->oss.channels != channels) {
runtime->oss.params = 1;
runtime->oss.channels = channels;
}
- mutex_unlock(&runtime->oss.params_lock);
+ unlock_params(runtime);
}
return snd_pcm_oss_get_channels(pcm_oss_file);
}
@@ -1896,6 +1915,7 @@ static int snd_pcm_oss_get_formats(struc
static int snd_pcm_oss_set_format(struct snd_pcm_oss_file *pcm_oss_file, int format)
{
int formats, idx;
+ int err;

if (format != AFMT_QUERY) {
formats = snd_pcm_oss_get_formats(pcm_oss_file);
@@ -1909,15 +1929,14 @@ static int snd_pcm_oss_set_format(struct
if (substream == NULL)
continue;
runtime = substream->runtime;
- if (atomic_read(&runtime->oss.rw_ref))
- return -EBUSY;
- if (mutex_lock_interruptible(&runtime->oss.params_lock))
- return -ERESTARTSYS;
+ err = lock_params(runtime);
+ if (err < 0)
+ return err;
if (runtime->oss.format != format) {
runtime->oss.params = 1;
runtime->oss.format = format;
}
- mutex_unlock(&runtime->oss.params_lock);
+ unlock_params(runtime);
}
}
return snd_pcm_oss_get_format(pcm_oss_file);
@@ -1965,12 +1984,11 @@ static int snd_pcm_oss_set_subdivide(str
if (substream == NULL)
continue;
runtime = substream->runtime;
- if (atomic_read(&runtime->oss.rw_ref))
- return -EBUSY;
- if (mutex_lock_interruptible(&runtime->oss.params_lock))
- return -ERESTARTSYS;
+ err = lock_params(runtime);
+ if (err < 0)
+ return err;
err = snd_pcm_oss_set_subdivide1(substream, subdivide);
- mutex_unlock(&runtime->oss.params_lock);
+ unlock_params(runtime);
if (err < 0)
return err;
}
@@ -2005,12 +2023,11 @@ static int snd_pcm_oss_set_fragment(stru
if (substream == NULL)
continue;
runtime = substream->runtime;
- if (atomic_read(&runtime->oss.rw_ref))
- return -EBUSY;
- if (mutex_lock_interruptible(&runtime->oss.params_lock))
- return -ERESTARTSYS;
+ err = lock_params(runtime);
+ if (err < 0)
+ return err;
err = snd_pcm_oss_set_fragment1(substream, val);
- mutex_unlock(&runtime->oss.params_lock);
+ unlock_params(runtime);
if (err < 0)
return err;
}