linux-cve-announce - CVE-2024-38600: ALSA: Fix deadlocks with kctl removals at disconnection

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Message-ID: <2024061957-CVE-2024-38600-aa7e@gregkh>
Date: Wed, 19 Jun 2024 15:46:06 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-38600: ALSA: Fix deadlocks with kctl removals at disconnection

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.

The Linux kernel CVE team has assigned CVE-2024-38600 to this issue.

Affected and fixed versions
===========================

	Fixed in 5.15.161 with commit ff80185e7b7b
	Fixed in 6.1.93 with commit c2fb439f4f14
	Fixed in 6.6.33 with commit 2f103287ef79
	Fixed in 6.8.12 with commit 88ce3fe255d5
	Fixed in 6.9.3 with commit 6b55e879e7bd
	Fixed in 6.10-rc1 with commit 87988a534d8e

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-38600
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	sound/core/init.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	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