linux-cve-announce - CVE-2024-26755: md: Don't suspend the array for interrupted reshape

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Date: Wed,  3 Apr 2024 19:31:22 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-26755: md: Don't suspend the array for interrupted reshape

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

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

md: Don't suspend the array for interrupted reshape

md_start_sync() will suspend the array if there are spares that can be
added or removed from conf, however, if reshape is still in progress,
this won't happen at all or data will be corrupted(remove_and_add_spares
won't be called from md_choose_sync_action for reshape), hence there is
no need to suspend the array if reshape is not done yet.

Meanwhile, there is a potential deadlock for raid456:

1) reshape is interrupted;

2) set one of the disk WantReplacement, and add a new disk to the array,
   however, recovery won't start until the reshape is finished;

3) then issue an IO across reshpae position, this IO will wait for
   reshape to make progress;

4) continue to reshape, then md_start_sync() found there is a spare disk
   that can be added to conf, mddev_suspend() is called;

Step 4 and step 3 is waiting for each other, deadlock triggered. Noted
this problem is found by code review, and it's not reporduced yet.

Fix this porblem by don't suspend the array for interrupted reshape,
this is safe because conf won't be changed until reshape is done.

The Linux kernel CVE team has assigned CVE-2024-26755 to this issue.

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

	Issue introduced in 6.7 with commit bc08041b32ab and fixed in 6.7.7 with commit 60d6130d0ac1
	Issue introduced in 6.7 with commit bc08041b32ab and fixed in 6.8 with commit 9e46c70e829b

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-2024-26755
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/md.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/60d6130d0ac1d883ed93c2a1e10aadb60967fd48
	https://git.kernel.org/stable/c/9e46c70e829bddc24e04f963471e9983a11598b7