Vulnerability CVE-2024-38600
Published: 2024-06-19

Description:
In the Linux kernel, the following vulnerability has been resolved:

ALSA: Fix deadlocks with kctl removals at disconnection

In snd_card_disconnect(), we set card->shutdown flag at the beginning,
call callbacks and do sync for card->power_ref_sleep waiters at the
end. The callback may delete a kctl element, and this can lead to a
deadlock when the device was in the suspended state. Namely:

* A process waits for the power up at snd_power_ref_and_wait() in
snd_ctl_info() or read/write() inside card->controls_rwsem.

* The system gets disconnected meanwhile, and the driver tries to
delete a kctl via snd_ctl_remove*(); it tries to take
card->controls_rwsem again, but this is already locked by the
above. Since the sleeper isn't woken up, this deadlocks.

An easy fix is to wake up sleepers before processing the driver
disconnect callbacks but right after setting the card->shutdown flag.
Then all sleepers will abort immediately, and the code flows again.

So, basically this patch moves the wait_event() call at the right
timing. While we're at it, just to be sure, call wait_event_all()
instead of wait_event(), although we don't use exclusive events on
this queue for now.

 References:
https://git.kernel.org/stable/c/ff80185e7b7b547a0911fcfc8aefc61c3e8304d7
https://git.kernel.org/stable/c/c2fb439f4f1425a961d20bec818fed2c2d9ef70a
https://git.kernel.org/stable/c/2f103287ef7960854808930499d1181bd0145d68
https://git.kernel.org/stable/c/88ce3fe255d58a93624b467af036dc3519f309c7
https://git.kernel.org/stable/c/6b55e879e7bd023a03888fc6c8339edf82f576f4
https://git.kernel.org/stable/c/87988a534d8e12f2e6fc01fe63e6c1925dc5307c
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