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@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
sound/core/seq/seq_timer.c | 14 +++++++++-----
1 file 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);
}
}
--
2.16.4
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