cve/published/2024/CVE-2024-39476.mbox

From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: <linux-cve-announce@vger.kernel.org>
Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: CVE-2024-39476: md/raid5: fix deadlock that raid5d() wait for itself to clear MD_SB_CHANGE_PENDING

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

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

md/raid5: fix deadlock that raid5d() wait for itself to clear MD_SB_CHANGE_PENDING

Xiao reported that lvm2 test lvconvert-raid-takeover.sh can hang with
small possibility, the root cause is exactly the same as commit
bed9e27baf52 ("Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d"")

However, Dan reported another hang after that, and junxiao investigated
the problem and found out that this is caused by plugged bio can't issue
from raid5d().

Current implementation in raid5d() has a weird dependence:

1) md_check_recovery() from raid5d() must hold 'reconfig_mutex' to clear
   MD_SB_CHANGE_PENDING;
2) raid5d() handles IO in a deadloop, until all IO are issued;
3) IO from raid5d() must wait for MD_SB_CHANGE_PENDING to be cleared;

This behaviour is introduce before v2.6, and for consequence, if other
context hold 'reconfig_mutex', and md_check_recovery() can't update
super_block, then raid5d() will waste one cpu 100% by the deadloop, until
'reconfig_mutex' is released.

Refer to the implementation from raid1 and raid10, fix this problem by
skipping issue IO if MD_SB_CHANGE_PENDING is still set after
md_check_recovery(), daemon thread will be woken up when 'reconfig_mutex'
is released. Meanwhile, the hang problem will be fixed as well.

The Linux kernel CVE team has assigned CVE-2024-39476 to this issue.


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

	Issue introduced in 4.19.262 with commit f3d55bd5b7b928ad82f8075d89c908702f3593ab and fixed in 4.19.316 with commit b32aa95843cac6b12c2c014d40fca18aef24a347
	Issue introduced in 5.4.220 with commit 1c00bb624cd084e2006520ad0edacaff0fb941c4 and fixed in 5.4.278 with commit 634ba3c97ec413cb10681c7b196db43ee461ecf4
	Issue introduced in 5.10.150 with commit 782b3e71c957991ac8ae53318bc369049d49bb53 and fixed in 5.10.219 with commit aa64464c8f4d2ab92f6d0b959a1e0767b829d787
	Issue introduced in 5.15.75 with commit 9e86dffd0b02594d2e7c60c6db9e889c0395414b and fixed in 5.15.161 with commit 098d54934814dd876963abfe751c3b1cf7fbe56a
	Issue introduced in 6.1 with commit 5e2cf333b7bd5d3e62595a44d598a254c697cd74 and fixed in 6.1.94 with commit 3f8d5e802d4cedd445f9a89be8c3fd2d0e99024b
	Issue introduced in 6.1 with commit 5e2cf333b7bd5d3e62595a44d598a254c697cd74 and fixed in 6.6.34 with commit cd2538e5af495b3c747e503db346470fc1ffc447
	Issue introduced in 6.1 with commit 5e2cf333b7bd5d3e62595a44d598a254c697cd74 and fixed in 6.9.5 with commit e332a12f65d8fed8cf63bedb4e9317bb872b9ac7
	Issue introduced in 6.1 with commit 5e2cf333b7bd5d3e62595a44d598a254c697cd74 and fixed in 6.10 with commit 151f66bb618d1fd0eeb84acb61b4a9fa5d8bb0fa
	Issue introduced in 4.14.296 with commit 7d808fe6af8409cf9f46ed2b10840e5788985e9b
	Issue introduced in 5.19.17 with commit 2cab058f2b147e0b7c01546ba00445e5701861f5
	Issue introduced in 6.0.3 with commit 91962e40ec3d26e291db230cd45b302da2aff200

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-2024-39476
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/md/raid5.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/b32aa95843cac6b12c2c014d40fca18aef24a347
	https://git.kernel.org/stable/c/634ba3c97ec413cb10681c7b196db43ee461ecf4
	https://git.kernel.org/stable/c/aa64464c8f4d2ab92f6d0b959a1e0767b829d787
	https://git.kernel.org/stable/c/098d54934814dd876963abfe751c3b1cf7fbe56a
	https://git.kernel.org/stable/c/3f8d5e802d4cedd445f9a89be8c3fd2d0e99024b
	https://git.kernel.org/stable/c/cd2538e5af495b3c747e503db346470fc1ffc447
	https://git.kernel.org/stable/c/e332a12f65d8fed8cf63bedb4e9317bb872b9ac7
	https://git.kernel.org/stable/c/151f66bb618d1fd0eeb84acb61b4a9fa5d8bb0fa