CVE-2026-68202

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ALSA: seq: close a re-opened queue timer in the destructor<br /> <br /> queue_delete() closes the queue timer, then frees it. snd_seq_timer_close()<br /> clears q-&gt;timer-&gt;timeri. snd_use_lock_sync() then drains borrowers, and<br /> snd_seq_timer_delete() frees q-&gt;timer.<br /> <br /> A borrower can re-open the timer inside that window. A SET_QUEUE_CLIENT<br /> that took a queueptr() use_lock reference before the queue was unlinked<br /> runs snd_seq_timer_open() after the close. Open refuses re-open only while<br /> timeri is set, and the close just cleared it, so it re-opens timeri.<br /> <br /> snd_seq_timer_delete() does not close that instance. Its snd_seq_timer_stop()<br /> is a no-op, because running was cleared first. So it frees q-&gt;timer with the<br /> instance still live. The queue is freed next.<br /> <br /> The instance stays on the global timer with callback_data pointing at the<br /> freed queue. A non-owner START on the unlocked queue arms it. The next tick<br /> derefs the freed queue in snd_seq_timer_interrupt().<br /> <br /> Reachable by an unprivileged user with access to /dev/snd/seq. No CAP and<br /> no queue ownership required.<br /> <br /> Close any lingering instance in the destructor. There, -&gt;timeri can no<br /> longer change: the queue is unlinked and all use_lock borrowers have<br /> drained, so no snd_seq_queue_use() can re-open it. Close it before clearing<br /> q-&gt;timer. snd_timer_close() waits for any in-flight snd_seq_timer_interrupt()<br /> to finish, and that callback still reads q-&gt;timer (via snd_seq_check_queue()),<br /> so q-&gt;timer must stay valid until it drains.