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ALSA: pcm: Return -EBUSY for OSS ioctls changing busy streams

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OSS PCM stream management isn't modal but it allows ioctls issued at
any time for changing the parameters.  In the previous hardening
patch ("ALSA: pcm: Avoid potential races between OSS ioctls and
read/write"), we covered these races and prevent the corruption by
protecting the concurrent accesses via params_lock mutex.  However,
this means that some ioctls that try to change the stream parameter
(e.g. channels or format) would be blocked until the read/write
finishes, and it may take really long.

Basically changing the parameter while reading/writing is an invalid
operation, hence it's even more user-friendly from the API POV if it
returns -EBUSY in such a situation.

This patch adds such checks in the relevant ioctls with the addition
of read/write access refcount.

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2018-03-23 08:03:26 +01:00
parent 02a5d6925c
commit 40cab6e88c
2 changed files with 28 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/sound/pcm_oss.h
View File

@ -57,6 +57,7 @@ struct snd_pcm_oss_runtime {
char *buffer; /* vmallocated period */
size_t buffer_used; /* used length from period buffer */
struct mutex params_lock;
atomic_t rw_ref; /* concurrent read/write accesses */
#ifdef CONFIG_SND_PCM_OSS_PLUGINS
struct snd_pcm_plugin *plugin_first;
struct snd_pcm_plugin *plugin_last;

36
sound/core/oss/pcm_oss.c
View File

@ -1370,6 +1370,7 @@ static ssize_t snd_pcm_oss_write1(struct snd_pcm_substream *substream, const cha
if (atomic_read(&substream->mmap_count))
return -ENXIO;
atomic_inc(&runtime->oss.rw_ref);
while (bytes > 0) {
if (mutex_lock_interruptible(&runtime->oss.params_lock)) {
tmp = -ERESTARTSYS;
@ -1433,6 +1434,7 @@ static ssize_t snd_pcm_oss_write1(struct snd_pcm_substream *substream, const cha
}
tmp = 0;
}
atomic_dec(&runtime->oss.rw_ref);
return xfer > 0 ? (snd_pcm_sframes_t)xfer : tmp;
}
@ -1478,6 +1480,7 @@ static ssize_t snd_pcm_oss_read1(struct snd_pcm_substream *substream, char __use
if (atomic_read(&substream->mmap_count))
return -ENXIO;
atomic_inc(&runtime->oss.rw_ref);
while (bytes > 0) {
if (mutex_lock_interruptible(&runtime->oss.params_lock)) {
tmp = -ERESTARTSYS;
@ -1526,6 +1529,7 @@ static ssize_t snd_pcm_oss_read1(struct snd_pcm_substream *substream, char __use
}
tmp = 0;
}
atomic_dec(&runtime->oss.rw_ref);
return xfer > 0 ? (snd_pcm_sframes_t)xfer : tmp;
}
@ -1632,8 +1636,11 @@ static int snd_pcm_oss_sync(struct snd_pcm_oss_file *pcm_oss_file)
goto __direct;
if ((err = snd_pcm_oss_make_ready(substream)) < 0)
return err;
if (mutex_lock_interruptible(&runtime->oss.params_lock))
atomic_inc(&runtime->oss.rw_ref);
if (mutex_lock_interruptible(&runtime->oss.params_lock)) {
atomic_dec(&runtime->oss.rw_ref);
return -ERESTARTSYS;
}
format = snd_pcm_oss_format_from(runtime->oss.format);
width = snd_pcm_format_physical_width(format);
if (runtime->oss.buffer_used > 0) {
@ -1645,10 +1652,8 @@ static int snd_pcm_oss_sync(struct snd_pcm_oss_file *pcm_oss_file)
runtime->oss.buffer + runtime->oss.buffer_used,
size);
err = snd_pcm_oss_sync1(substream, runtime->oss.period_bytes);
if (err < 0) {
mutex_unlock(&runtime->oss.params_lock);
return err;
}
if (err < 0)
goto unlock;
} else if (runtime->oss.period_ptr > 0) {
#ifdef OSS_DEBUG
pcm_dbg(substream->pcm, "sync: period_ptr\n");
@ -1658,10 +1663,8 @@ static int snd_pcm_oss_sync(struct snd_pcm_oss_file *pcm_oss_file)
runtime->oss.buffer,
size * 8 / width);
err = snd_pcm_oss_sync1(substream, size);
if (err < 0) {
mutex_unlock(&runtime->oss.params_lock);
return err;
}
if (err < 0)
goto unlock;
}
/*
* The ALSA's period might be a bit large than OSS one.
@ -1675,7 +1678,11 @@ static int snd_pcm_oss_sync(struct snd_pcm_oss_file *pcm_oss_file)
else if (runtime->access == SNDRV_PCM_ACCESS_RW_NONINTERLEAVED)
snd_pcm_lib_writev(substream, NULL, size);
}
unlock:
mutex_unlock(&runtime->oss.params_lock);
atomic_dec(&runtime->oss.rw_ref);
if (err < 0)
return err;
/*
* finish sync: drain the buffer
*/
@ -1723,6 +1730,8 @@ static int snd_pcm_oss_set_rate(struct snd_pcm_oss_file *pcm_oss_file, int rate)
rate = 192000;
if (mutex_lock_interruptible(&runtime->oss.params_lock))
return -ERESTARTSYS;
if (atomic_read(&runtime->oss.rw_ref))
return -EBUSY;
if (runtime->oss.rate != rate) {
runtime->oss.params = 1;
runtime->oss.rate = rate;
@ -1757,6 +1766,8 @@ static int snd_pcm_oss_set_channels(struct snd_pcm_oss_file *pcm_oss_file, unsig
runtime = substream->runtime;
if (mutex_lock_interruptible(&runtime->oss.params_lock))
return -ERESTARTSYS;
if (atomic_read(&runtime->oss.rw_ref))
return -EBUSY;
if (runtime->oss.channels != channels) {
runtime->oss.params = 1;
runtime->oss.channels = channels;
@ -1847,6 +1858,8 @@ 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;
if (runtime->oss.format != format) {
@ -1901,6 +1914,8 @@ 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 = snd_pcm_oss_set_subdivide1(substream, subdivide);
@ -1939,6 +1954,8 @@ 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 = snd_pcm_oss_set_fragment1(substream, val);
@ -2333,6 +2350,7 @@ static void snd_pcm_oss_init_substream(struct snd_pcm_substream *substream,
runtime->oss.maxfrags = 0;
runtime->oss.subdivision = 0;
substream->pcm_release = snd_pcm_oss_release_substream;
atomic_set(&runtime->oss.rw_ref, 0);
}
static int snd_pcm_oss_release_file(struct snd_pcm_oss_file *pcm_oss_file)