linux-cve-announce - CVE-2024-26899: block: fix deadlock between bd_link_disk

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Message-ID: <2024041745-CVE-2024-26899-3f41@gregkh>
Date: Wed, 17 Apr 2024 12:29:14 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-26899: block: fix deadlock between bd_link_disk_holder and partition scan

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

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

block: fix deadlock between bd_link_disk_holder and partition scan

'open_mutex' of gendisk is used to protect open/close block devices. But
in bd_link_disk_holder(), it is used to protect the creation of symlink
between holding disk and slave bdev, which introduces some issues.

When bd_link_disk_holder() is called, the driver is usually in the process
of initialization/modification and may suspend submitting io. At this
time, any io hold 'open_mutex', such as scanning partitions, can cause
deadlocks. For example, in raid:

T1                              T2
bdev_open_by_dev
 lock open_mutex [1]
 ...
  efi_partition
  ...
   md_submit_bio
				md_ioctl mddev_syspend
				  -> suspend all io
				 md_add_new_disk
				  bind_rdev_to_array
				   bd_link_disk_holder
				    try lock open_mutex [2]
    md_handle_request
     -> wait mddev_resume

T1 scan partition, T2 add a new device to raid. T1 waits for T2 to resume
mddev, but T2 waits for open_mutex held by T1. Deadlock occurs.

Fix it by introducing a local mutex 'blk_holder_mutex' to replace
'open_mutex'.

The Linux kernel CVE team has assigned CVE-2024-26899 to this issue.


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

	Issue introduced in 6.7 with commit 1b0a2d950ee2 and fixed in 6.7.11 with commit 1e5c5b0abaee
	Issue introduced in 6.7 with commit 1b0a2d950ee2 and fixed in 6.8.2 with commit 5a87c1f7993b
	Issue introduced in 6.7 with commit 1b0a2d950ee2 and fixed in 6.9-rc1 with commit 03f12122b20b

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-2024-26899
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/holder.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/1e5c5b0abaee7b62a10b9707a62083b71ad21f62
	https://git.kernel.org/stable/c/5a87c1f7993bc8ac358a3766bac5dc7126e01e98
	https://git.kernel.org/stable/c/03f12122b20b6e6028e9ed69030a49f9cffcbb75