There is a small race window at snd_pcm_oss_set_trigger() that is
called from OSS PCM SNDCTL_DSP_SETTRIGGER ioctl; namely the function
calls snd_pcm_oss_make_ready() at first, then takes the params_lock
mutex for the rest. When the stream is set up again by another thread
between them, it leads to inconsistency, and may result in unexpected
results such as NULL dereference of OSS buffer as a fuzzer spotted
recently.
The fix is simply to cover snd_pcm_oss_make_ready() call into the same
params_lock mutex with snd_pcm_oss_make_ready_locked() variant.
Signed-off-by: Ma Ke <make_ruc2021@xxxxxxx>
---
sound/core/oss/pcm_oss.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 728c211142d1..f6340a2fe52b 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -2083,21 +2083,15 @@ static int snd_pcm_oss_set_trigger(struct snd_pcm_oss_file *pcm_oss_file, int tr
psubstream = pcm_oss_file->streams[SNDRV_PCM_STREAM_PLAYBACK];
csubstream = pcm_oss_file->streams[SNDRV_PCM_STREAM_CAPTURE];
- if (psubstream) {
- err = snd_pcm_oss_make_ready(psubstream);
- if (err < 0)
- return err;
- }
- if (csubstream) {
- err = snd_pcm_oss_make_ready(csubstream);
- if (err < 0)
- return err;
- }
if (psubstream) {
runtime = psubstream->runtime;
cmd = 0;
if (mutex_lock_interruptible(&runtime->oss.params_lock))
return -ERESTARTSYS;
+ err = snd_pcm_oss_make_ready_locked(psubstream);
+ if (err < 0)
+ mutex_unlock(&runtime->oss.params_lock);
+ return err;
if (trigger & PCM_ENABLE_OUTPUT) {
if (runtime->oss.trigger)
goto _skip1;
@@ -2128,6 +2122,10 @@ static int snd_pcm_oss_set_trigger(struct snd_pcm_oss_file *pcm_oss_file, int tr
cmd = 0;
if (mutex_lock_interruptible(&runtime->oss.params_lock))
return -ERESTARTSYS;
+ err = snd_pcm_oss_make_ready_locked(csubstream);
+ if (err < 0)
+ mutex_unlock(&runtime->oss.params_lock);
+ return err;
if (trigger & PCM_ENABLE_INPUT) {
if (runtime->oss.trigger)
goto _skip2;
--
2.37.2
