diff options
| author | Takashi Iwai <tiwai@suse.de> | 2020-01-15 21:37:33 +0100 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2020-01-15 21:38:18 +0100 |
| commit | 60adcfde92fa40fcb2dbf7cc52f9b096e0cd109a (patch) | |
| tree | 5d14b22d1dc22cee63d066961c1bf30dd6c8ee85 | |
| parent | 5d1b71226dc4d44b4b65766fa9d74492f9d4587b (diff) | |
ALSA: seq: Fix racy access for queue timer in proc read
snd_seq_info_timer_read() reads the information of the timer assigned
for each queue, but it's done in a racy way which may lead to UAF as
spotted by syzkaller.
This patch applies the missing q->timer_mutex lock while accessing the
timer object as well as a slight code change to adapt the standard
coding style.
Reported-by: syzbot+2b2ef983f973e5c40943@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200115203733.26530-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
| -rw-r--r-- | sound/core/seq/seq_timer.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/sound/core/seq/seq_timer.c b/sound/core/seq/seq_timer.c index 63dc7bdb622d..be59b59c9be4 100644 --- a/sound/core/seq/seq_timer.c +++ b/sound/core/seq/seq_timer.c @@ -471,15 +471,19 @@ void snd_seq_info_timer_read(struct snd_info_entry *entry, q = queueptr(idx); if (q == NULL) continue; - if ((tmr = q->timer) == NULL || - (ti = tmr->timeri) == NULL) { - queuefree(q); - continue; - } + mutex_lock(&q->timer_mutex); + tmr = q->timer; + if (!tmr) + goto unlock; + ti = tmr->timeri; + if (!ti) + goto unlock; snd_iprintf(buffer, "Timer for queue %i : %s\n", q->queue, ti->timer->name); resolution = snd_timer_resolution(ti) * tmr->ticks; snd_iprintf(buffer, " Period time : %lu.%09lu\n", resolution / 1000000000, resolution % 1000000000); snd_iprintf(buffer, " Skew : %u / %u\n", tmr->skew, tmr->skew_base); +unlock: + mutex_unlock(&q->timer_mutex); queuefree(q); } } |