linux-cve-announce - CVE-2023-53045: usb: gadget: u_audio: don't let userspace block driver unbind

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Message-ID: <2025050204-CVE-2023-53045-351a@gregkh>
Date: Fri,  2 May 2025 17:55:10 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53045: usb: gadget: u_audio: don't let userspace block driver unbind

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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

usb: gadget: u_audio: don't let userspace block driver unbind

In the unbind callback for f_uac1 and f_uac2, a call to snd_card_free()
via g_audio_cleanup() will disconnect the card and then wait for all
resources to be released, which happens when the refcount falls to zero.
Since userspace can keep the refcount incremented by not closing the
relevant file descriptor, the call to unbind may block indefinitely.
This can cause a deadlock during reboot, as evidenced by the following
blocked task observed on my machine:

  task:reboot  state:D stack:0   pid:2827  ppid:569    flags:0x0000000c
  Call trace:
   __switch_to+0xc8/0x140
   __schedule+0x2f0/0x7c0
   schedule+0x60/0xd0
   schedule_timeout+0x180/0x1d4
   wait_for_completion+0x78/0x180
   snd_card_free+0x90/0xa0
   g_audio_cleanup+0x2c/0x64
   afunc_unbind+0x28/0x60
   ...
   kernel_restart+0x4c/0xac
   __do_sys_reboot+0xcc/0x1ec
   __arm64_sys_reboot+0x28/0x30
   invoke_syscall+0x4c/0x110
   ...

The issue can also be observed by opening the card with arecord and
then stopping the process through the shell before unbinding:

  # arecord -D hw:UAC2Gadget -f S32_LE -c 2 -r 48000 /dev/null
  Recording WAVE '/dev/null' : Signed 32 bit Little Endian, Rate 48000 Hz, Stereo
  ^Z[1]+  Stopped                    arecord -D hw:UAC2Gadget -f S32_LE -c 2 -r 48000 /dev/null
  # echo gadget.0 > /sys/bus/gadget/drivers/configfs-gadget/unbind
  (observe that the unbind command never finishes)

Fix the problem by using snd_card_free_when_closed() instead, which will
still disconnect the card as desired, but defer the task of freeing the
resources to the core once userspace closes its file descriptor.

The Linux kernel CVE team has assigned CVE-2023-53045 to this issue.


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

	Issue introduced in 3.4 with commit 132fcb460839a876f5bc8b71bede60f8d0875757 and fixed in 4.14.312 with commit 3e016ef2e72da93a2ea7afbb45de1b481b44d761
	Issue introduced in 3.4 with commit 132fcb460839a876f5bc8b71bede60f8d0875757 and fixed in 4.19.280 with commit 3256e152b645fc1e788ba44c2d8ced690113e3e6
	Issue introduced in 3.4 with commit 132fcb460839a876f5bc8b71bede60f8d0875757 and fixed in 5.4.240 with commit 0eda2004f38d95ef5715d62be884cd344260535b
	Issue introduced in 3.4 with commit 132fcb460839a876f5bc8b71bede60f8d0875757 and fixed in 5.10.177 with commit 33f341c1fc60e172a3515c51bdabee11e83d1ee9
	Issue introduced in 3.4 with commit 132fcb460839a876f5bc8b71bede60f8d0875757 and fixed in 5.15.105 with commit b131989797f7287d7fdadb2bababc05a15d44750
	Issue introduced in 3.4 with commit 132fcb460839a876f5bc8b71bede60f8d0875757 and fixed in 6.1.22 with commit 3bc7324e4911351e39c54a62e6ca46321cb10faf
	Issue introduced in 3.4 with commit 132fcb460839a876f5bc8b71bede60f8d0875757 and fixed in 6.2.9 with commit 43ca70753dfffd517d2af126da28690f8f615605
	Issue introduced in 3.4 with commit 132fcb460839a876f5bc8b71bede60f8d0875757 and fixed in 6.3 with commit 6c67ed9ad9b83e453e808f9b31a931a20a25629b

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-2023-53045
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:
	drivers/usb/gadget/function/u_audio.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/3e016ef2e72da93a2ea7afbb45de1b481b44d761
	https://git.kernel.org/stable/c/3256e152b645fc1e788ba44c2d8ced690113e3e6
	https://git.kernel.org/stable/c/0eda2004f38d95ef5715d62be884cd344260535b
	https://git.kernel.org/stable/c/33f341c1fc60e172a3515c51bdabee11e83d1ee9
	https://git.kernel.org/stable/c/b131989797f7287d7fdadb2bababc05a15d44750
	https://git.kernel.org/stable/c/3bc7324e4911351e39c54a62e6ca46321cb10faf
	https://git.kernel.org/stable/c/43ca70753dfffd517d2af126da28690f8f615605
	https://git.kernel.org/stable/c/6c67ed9ad9b83e453e808f9b31a931a20a25629b