linux-cve-announce - CVE-2023-53455: drm/vc4: drop all currently held locks if deadlock happens

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Message-ID: <2025100104-CVE-2023-53455-3efb@gregkh>
Date: Wed,  1 Oct 2025 13:42:25 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53455: drm/vc4: drop all currently held locks if deadlock happens

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

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

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

drm/vc4: drop all currently held locks if deadlock happens

If vc4_hdmi_reset_link() returns -EDEADLK, it means that a deadlock
happened in the locking context. This situation should be addressed by
dropping all currently held locks and block until the contended lock
becomes available. Currently, vc4 is not dealing with the deadlock
properly, producing the following output when PROVE_LOCKING is enabled:

[  825.612809] ------------[ cut here ]------------
[  825.612852] WARNING: CPU: 1 PID: 116 at drivers/gpu/drm/drm_modeset_lock.c:276 drm_modeset_drop_locks+0x60/0x68 [drm]
[  825.613458] Modules linked in: 8021q mrp garp stp llc
raspberrypi_cpufreq brcmfmac brcmutil crct10dif_ce hci_uart cfg80211
btqca btbcm bluetooth vc4 raspberrypi_hwmon snd_soc_hdmi_codec cec
clk_raspberrypi ecdh_generic drm_display_helper ecc rfkill
drm_dma_helper drm_kms_helper pwm_bcm2835 bcm2835_thermal bcm2835_rng
rng_core i2c_bcm2835 drm fuse ip_tables x_tables ipv6
[  825.613735] CPU: 1 PID: 116 Comm: kworker/1:2 Tainted: G        W 6.1.0-rc6-01399-g941aae326315 #3
[  825.613759] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
[  825.613777] Workqueue: events output_poll_execute [drm_kms_helper]
[  825.614038] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[  825.614063] pc : drm_modeset_drop_locks+0x60/0x68 [drm]
[  825.614603] lr : drm_helper_probe_detect+0x120/0x1b4 [drm_kms_helper]
[  825.614829] sp : ffff800008313bf0
[  825.614844] x29: ffff800008313bf0 x28: ffffcd7778b8b000 x27: 0000000000000000
[  825.614883] x26: 0000000000000001 x25: 0000000000000001 x24: ffff677cc35c2758
[  825.614920] x23: ffffcd7707d01430 x22: ffffcd7707c3edc7 x21: 0000000000000001
[  825.614958] x20: 0000000000000000 x19: ffff800008313c10 x18: 000000000000b6d3
[  825.614995] x17: ffffcd777835e214 x16: ffffcd7777cef870 x15: fffff81000000000
[  825.615033] x14: 0000000000000000 x13: 0000000000000099 x12: 0000000000000002
[  825.615070] x11: 72917988020af800 x10: 72917988020af800 x9 : 72917988020af800
[  825.615108] x8 : ffff677cc665e0a8 x7 : d00a8c180000110c x6 : ffffcd77774c0054
[  825.615145] x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
[  825.615181] x2 : ffff677cc55e1880 x1 : ffffcd7777cef8ec x0 : ffff800008313c10
[  825.615219] Call trace:
[  825.615232]  drm_modeset_drop_locks+0x60/0x68 [drm]
[  825.615773]  drm_helper_probe_detect+0x120/0x1b4 [drm_kms_helper]
[  825.616003]  output_poll_execute+0xe4/0x224 [drm_kms_helper]
[  825.616233]  process_one_work+0x2b4/0x618
[  825.616264]  worker_thread+0x24c/0x464
[  825.616288]  kthread+0xec/0x110
[  825.616310]  ret_from_fork+0x10/0x20
[  825.616335] irq event stamp: 7634
[  825.616349] hardirqs last  enabled at (7633): [<ffffcd777831ee90>] _raw_spin_unlock_irq+0x3c/0x78
[  825.616384] hardirqs last disabled at (7634): [<ffffcd7778315a78>] __schedule+0x134/0x9f0
[  825.616411] softirqs last  enabled at (7630): [<ffffcd7707aacea0>] local_bh_enable+0x4/0x30 [ipv6]
[  825.617019] softirqs last disabled at (7618): [<ffffcd7707aace70>] local_bh_disable+0x4/0x30 [ipv6]
[  825.617586] ---[ end trace 0000000000000000 ]---

Therefore, deal with the deadlock as suggested by [1], using the
function drm_modeset_backoff().

[1] https://docs.kernel.org/gpu/drm-kms.html?highlight=kms#kms-locking

The Linux kernel CVE team has assigned CVE-2023-53455 to this issue.


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

	Issue introduced in 6.1 with commit 6bed2ea3cb3856edf37cca20753e689ee8774793 and fixed in 6.1.16 with commit 41286a53e7f54202fd277cd516724de3ab7497c7
	Issue introduced in 6.1 with commit 6bed2ea3cb3856edf37cca20753e689ee8774793 and fixed in 6.2.3 with commit f483eda89a2e717daa7b15c8ca228a209f65617b
	Issue introduced in 6.1 with commit 6bed2ea3cb3856edf37cca20753e689ee8774793 and fixed in 6.3 with commit 479d4f0be4237ba33bc9432787aeb62c90e30f95

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-2023-53455
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/gpu/drm/vc4/vc4_hdmi.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/41286a53e7f54202fd277cd516724de3ab7497c7
	https://git.kernel.org/stable/c/f483eda89a2e717daa7b15c8ca228a209f65617b
	https://git.kernel.org/stable/c/479d4f0be4237ba33bc9432787aeb62c90e30f95