ALSA: pcm: Fix mutex unbalance in OSS emulation ioctls

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 702bfcc..5cc65d1 100644 (file)
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -834,6 +834,23 @@ static int choose_rate(struct snd_pcm_substream *substream,
        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)
 {
@@ -1773,6 +1790,8 @@ static int snd_pcm_oss_set_rate(struct snd_pcm_oss_file *pcm_oss_file, int rate)
        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;
@@ -1780,15 +1799,14 @@ 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;
+               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);
 }
@@ -1813,18 +1831,19 @@ static int snd_pcm_oss_set_channels(struct snd_pcm_oss_file *pcm_oss_file, unsig
        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);
 }
@@ -1897,6 +1916,7 @@ static int snd_pcm_oss_get_formats(struct snd_pcm_oss_file *pcm_oss_file)
 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);
@@ -1910,15 +1930,14 @@ static int snd_pcm_oss_set_format(struct snd_pcm_oss_file *pcm_oss_file, int for
                        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);
@@ -1966,12 +1985,11 @@ static int snd_pcm_oss_set_subdivide(struct snd_pcm_oss_file *pcm_oss_file, int
                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;
        }
@@ -2006,12 +2024,11 @@ static int snd_pcm_oss_set_fragment(struct snd_pcm_oss_file *pcm_oss_file, unsig
                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;
        }