linux-cve-announce - CVE-2025-40125: blk-mq: check kobject state_in_sysfs before deleting in blk_mq_unregister

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Message-ID: <2025111253-CVE-2025-40125-cb33@gregkh>
Date: Wed, 12 Nov 2025 19:24:01 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40125: blk-mq: check kobject state_in_sysfs before deleting in blk_mq_unregister_hctx

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

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

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

blk-mq: check kobject state_in_sysfs before deleting in blk_mq_unregister_hctx

In __blk_mq_update_nr_hw_queues() the return value of
blk_mq_sysfs_register_hctxs() is not checked. If sysfs creation for hctx
fails, later changing the number of hw_queues or removing disk will
trigger the following warning:

  kernfs: can not remove 'nr_tags', no directory
  WARNING: CPU: 2 PID: 637 at fs/kernfs/dir.c:1707 kernfs_remove_by_name_ns+0x13f/0x160
  Call Trace:
   remove_files.isra.1+0x38/0xb0
   sysfs_remove_group+0x4d/0x100
   sysfs_remove_groups+0x31/0x60
   __kobject_del+0x23/0xf0
   kobject_del+0x17/0x40
   blk_mq_unregister_hctx+0x5d/0x80
   blk_mq_sysfs_unregister_hctxs+0x94/0xd0
   blk_mq_update_nr_hw_queues+0x124/0x760
   nullb_update_nr_hw_queues+0x71/0xf0 [null_blk]
   nullb_device_submit_queues_store+0x92/0x120 [null_blk]

kobjct_del() was called unconditionally even if sysfs creation failed.
Fix it by checkig the kobject creation statusbefore deleting it.

The Linux kernel CVE team has assigned CVE-2025-40125 to this issue.


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

	Issue introduced in 4.20 with commit 477e19dedc9d3e1f4443a1d4ae00572a988120ea and fixed in 5.4.301 with commit a8c53553f1833cc2d14175d2d72cf37193a01898
	Issue introduced in 4.20 with commit 477e19dedc9d3e1f4443a1d4ae00572a988120ea and fixed in 5.10.246 with commit cc14ea21c4e658814d737ed4dedde6cd626a15ad
	Issue introduced in 4.20 with commit 477e19dedc9d3e1f4443a1d4ae00572a988120ea and fixed in 5.15.195 with commit 4b97e99b87a773d52699521d40864f3ec888e9a6
	Issue introduced in 4.20 with commit 477e19dedc9d3e1f4443a1d4ae00572a988120ea and fixed in 6.1.156 with commit 6e7dadc5763c48eb3b9b91265a21f312599ebb2c
	Issue introduced in 4.20 with commit 477e19dedc9d3e1f4443a1d4ae00572a988120ea and fixed in 6.6.112 with commit 06c4826b1d900611096e4621e93133db57e13911
	Issue introduced in 4.20 with commit 477e19dedc9d3e1f4443a1d4ae00572a988120ea and fixed in 6.12.53 with commit babc634e9fe2803962dba98a07587e835dbc0731
	Issue introduced in 4.20 with commit 477e19dedc9d3e1f4443a1d4ae00572a988120ea and fixed in 6.17.3 with commit d5ddd76ee52bdc16e9f8b1e7791291e785dab032
	Issue introduced in 4.20 with commit 477e19dedc9d3e1f4443a1d4ae00572a988120ea and fixed in 6.18-rc1 with commit 4c7ef92f6d4d08a27d676e4c348f4e2922cab3ed

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-2025-40125
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:
	block/blk-mq-sysfs.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/a8c53553f1833cc2d14175d2d72cf37193a01898
	https://git.kernel.org/stable/c/cc14ea21c4e658814d737ed4dedde6cd626a15ad
	https://git.kernel.org/stable/c/4b97e99b87a773d52699521d40864f3ec888e9a6
	https://git.kernel.org/stable/c/6e7dadc5763c48eb3b9b91265a21f312599ebb2c
	https://git.kernel.org/stable/c/06c4826b1d900611096e4621e93133db57e13911
	https://git.kernel.org/stable/c/babc634e9fe2803962dba98a07587e835dbc0731
	https://git.kernel.org/stable/c/d5ddd76ee52bdc16e9f8b1e7791291e785dab032
	https://git.kernel.org/stable/c/4c7ef92f6d4d08a27d676e4c348f4e2922cab3ed