On Thu, 21 Sep 2023 08:42:58 +0200, Ma Ke wrote:
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@163.com
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;
This breaks totally; you missed braces... (Ditto for another place).
Takashi
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;-- 2.37.2