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 --- include/sound/pcm_oss.h | 1 + sound/core/oss/pcm_oss.c | 36 +++++++++++++++++++++++++++--------- 2 files changed, 28 insertions(+), 9 deletions(-)
diff --git a/include/sound/pcm_oss.h b/include/sound/pcm_oss.h index 760c969d885d..a5b5575c59dd 100644 --- a/include/sound/pcm_oss.h +++ b/include/sound/pcm_oss.h @@ -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; diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c index f8bfee8022e0..a9082f219561 100644 --- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -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)