linux-cve-announce - CVE-2025-68310: s390/pci: Avoid deadlock between PCI error recovery and mlx5 crdump

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Message-ID: <2025121653-CVE-2025-68310-e0fc@gregkh>
Date: Tue, 16 Dec 2025 16:39:53 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68310: s390/pci: Avoid deadlock between PCI error recovery and mlx5 crdump

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

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

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

s390/pci: Avoid deadlock between PCI error recovery and mlx5 crdump

Do not block PCI config accesses through pci_cfg_access_lock() when
executing the s390 variant of PCI error recovery: Acquire just
device_lock() instead of pci_dev_lock() as powerpc's EEH and
generig PCI AER processing do.

During error recovery testing a pair of tasks was reported to be hung:

mlx5_core 0000:00:00.1: mlx5_health_try_recover:338:(pid 5553): health recovery flow aborted, PCI reads still not working
INFO: task kmcheck:72 blocked for more than 122 seconds.
      Not tainted 5.14.0-570.12.1.bringup7.el9.s390x #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kmcheck         state:D stack:0     pid:72    tgid:72    ppid:2      flags:0x00000000
Call Trace:
 [<000000065256f030>] __schedule+0x2a0/0x590
 [<000000065256f356>] schedule+0x36/0xe0
 [<000000065256f572>] schedule_preempt_disabled+0x22/0x30
 [<0000000652570a94>] __mutex_lock.constprop.0+0x484/0x8a8
 [<000003ff800673a4>] mlx5_unload_one+0x34/0x58 [mlx5_core]
 [<000003ff8006745c>] mlx5_pci_err_detected+0x94/0x140 [mlx5_core]
 [<0000000652556c5a>] zpci_event_attempt_error_recovery+0xf2/0x398
 [<0000000651b9184a>] __zpci_event_error+0x23a/0x2c0
INFO: task kworker/u1664:6:1514 blocked for more than 122 seconds.
      Not tainted 5.14.0-570.12.1.bringup7.el9.s390x #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u1664:6 state:D stack:0     pid:1514  tgid:1514  ppid:2      flags:0x00000000
Workqueue: mlx5_health0000:00:00.0 mlx5_fw_fatal_reporter_err_work [mlx5_core]
Call Trace:
 [<000000065256f030>] __schedule+0x2a0/0x590
 [<000000065256f356>] schedule+0x36/0xe0
 [<0000000652172e28>] pci_wait_cfg+0x80/0xe8
 [<0000000652172f94>] pci_cfg_access_lock+0x74/0x88
 [<000003ff800916b6>] mlx5_vsc_gw_lock+0x36/0x178 [mlx5_core]
 [<000003ff80098824>] mlx5_crdump_collect+0x34/0x1c8 [mlx5_core]
 [<000003ff80074b62>] mlx5_fw_fatal_reporter_dump+0x6a/0xe8 [mlx5_core]
 [<0000000652512242>] devlink_health_do_dump.part.0+0x82/0x168
 [<0000000652513212>] devlink_health_report+0x19a/0x230
 [<000003ff80075a12>] mlx5_fw_fatal_reporter_err_work+0xba/0x1b0 [mlx5_core]

No kernel log of the exact same error with an upstream kernel is
available - but the very same deadlock situation can be constructed there,
too:

- task: kmcheck
  mlx5_unload_one() tries to acquire devlink lock while the PCI error
  recovery code has set pdev->block_cfg_access by way of
  pci_cfg_access_lock()
- task: kworker
  mlx5_crdump_collect() tries to set block_cfg_access through
  pci_cfg_access_lock() while devlink_health_report() had acquired
  the devlink lock.

A similar deadlock situation can be reproduced by requesting a
crdump with
  > devlink health dump show pci/<BDF> reporter fw_fatal

while PCI error recovery is executed on the same <BDF> physical function
by mlx5_core's pci_error_handlers. On s390 this can be injected with
  > zpcictl --reset-fw <BDF>

Tests with this patch failed to reproduce that second deadlock situation,
the devlink command is rejected with "kernel answers: Permission denied" -
and we get a kernel log message of:

mlx5_core 1ed0:00:00.1: mlx5_crdump_collect:50:(pid 254382): crdump: failed to lock vsc gw err -5

because the config read of VSC_SEMAPHORE is rejected by the underlying
hardware.

Two prior attempts to address this issue have been discussed and
ultimately rejected [see link], with the primary argument that s390's
implementation of PCI error recovery is imposing restrictions that
neither powerpc's EEH nor PCI AER handling need. Tests show that PCI
error recovery on s390 is running to completion even without blocking
access to PCI config space.

The Linux kernel CVE team has assigned CVE-2025-68310 to this issue.


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

	Issue introduced in 5.16 with commit 4cdf2f4e24ff0d345fc36ef6d6aec059333a261e and fixed in 6.1.159 with commit d0df2503bc3c2be385ca2fd96585daad1870c7c5
	Issue introduced in 5.16 with commit 4cdf2f4e24ff0d345fc36ef6d6aec059333a261e and fixed in 6.6.117 with commit b63c061be622b17b495cbf78a6d5f2d4c3147f8e
	Issue introduced in 5.16 with commit 4cdf2f4e24ff0d345fc36ef6d6aec059333a261e and fixed in 6.12.58 with commit 3591d56ea9bfd3e7fbbe70f749bdeed689d415f9
	Issue introduced in 5.16 with commit 4cdf2f4e24ff0d345fc36ef6d6aec059333a261e and fixed in 6.17.8 with commit 54f938d9f5693af8ed586a08db4af5d9da1f0f2d
	Issue introduced in 5.16 with commit 4cdf2f4e24ff0d345fc36ef6d6aec059333a261e and fixed in 6.18 with commit 0fd20f65df6aa430454a0deed8f43efa91c54835

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-2025-68310
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:
	arch/s390/pci/pci_event.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/d0df2503bc3c2be385ca2fd96585daad1870c7c5
	https://git.kernel.org/stable/c/b63c061be622b17b495cbf78a6d5f2d4c3147f8e
	https://git.kernel.org/stable/c/3591d56ea9bfd3e7fbbe70f749bdeed689d415f9
	https://git.kernel.org/stable/c/54f938d9f5693af8ed586a08db4af5d9da1f0f2d
	https://git.kernel.org/stable/c/0fd20f65df6aa430454a0deed8f43efa91c54835