diff options
| author |   Norbert Szetei <norbert@doyensec.com> | 2026-07-14 10:29:23 +0200 |
|---|---|---|
| committer |   Takashi Iwai <tiwai@suse.de> | 2026-07-14 11:08:59 +0200 |
| commit | 2c4dc0ed50b05cd847a4b34b8cebf0775f19aeb9 (patch) | |
| tree | 0ff83eb1a959c6532b1099b4667e55fe6ac39d24 | |
| parent | ALSA: usb-audio: Add delay quirk for iBasso DC-Elite (diff) | |
ALSA: seq: close a re-opened queue timer in the destructor
queue_delete() closes the queue timer, then frees it. snd_seq_timer_close()
clears q->timer->timeri. snd_use_lock_sync() then drains borrowers, and
snd_seq_timer_delete() frees q->timer.
A borrower can re-open the timer inside that window. A SET_QUEUE_CLIENT
that took a queueptr() use_lock reference before the queue was unlinked
runs snd_seq_timer_open() after the close. Open refuses re-open only while
timeri is set, and the close just cleared it, so it re-opens timeri.
snd_seq_timer_delete() does not close that instance. Its snd_seq_timer_stop()
is a no-op, because running was cleared first. So it frees q->timer with the
instance still live. The queue is freed next.
The instance stays on the global timer with callback_data pointing at the
freed queue. A non-owner START on the unlocked queue arms it. The next tick
derefs the freed queue in snd_seq_timer_interrupt().
Reachable by an unprivileged user with access to /dev/snd/seq. No CAP and
no queue ownership required.
Close any lingering instance in the destructor. There, ->timeri can no
longer change: the queue is unlinked and all use_lock borrowers have
drained, so no snd_seq_queue_use() can re-open it. Close it before clearing
q->timer. snd_timer_close() waits for any in-flight snd_seq_timer_interrupt()
to finish, and that callback still reads q->timer (via snd_seq_check_queue()),
so q->timer must stay valid until it drains.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Norbert Szetei <norbert@doyensec.com>
Link: https://patch.msgid.link/422FDB81-2A68-47C7-A22D-2D3301E2E86D@doyensec.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
| -rw-r--r-- | sound/core/seq/seq_timer.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/sound/core/seq/seq_timer.c b/sound/core/seq/seq_timer.c index 4cd7211ccf48..419288eec4bb 100644 --- a/sound/core/seq/seq_timer.c +++ b/sound/core/seq/seq_timer.c @@ -61,12 +61,23 @@ struct snd_seq_timer *snd_seq_timer_new(void) void snd_seq_timer_delete(struct snd_seq_timer **tmr) { struct snd_seq_timer *t = *tmr; - *tmr = NULL; + struct snd_timer_instance *ti; if (t == NULL) { pr_debug("ALSA: seq: snd_seq_timer_delete() called with NULL timer\n"); return; } + + scoped_guard(spinlock_irq, &t->lock) { + ti = t->timeri; + t->timeri = NULL; + } + if (ti) { + snd_timer_close(ti); + snd_timer_instance_free(ti); + } + + *tmr = NULL; t->running = 0; /* reset time */ |