linux-cve-announce - CVE-2023-53665: md: don't dereference mddev after export

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Message-ID: <2025100704-CVE-2023-53665-3411@gregkh>
Date: Tue,  7 Oct 2025 17:21:24 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53665: md: don't dereference mddev after export_rdev()

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

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

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

md: don't dereference mddev after export_rdev()

Except for initial reference, mddev->kobject is referenced by
rdev->kobject, and if the last rdev is freed, there is no guarantee that
mddev is still valid. Hence mddev should not be used anymore after
export_rdev().

This problem can be triggered by following test for mdadm at very
low rate:

New file: mdadm/tests/23rdev-lifetime

devname=${dev0##*/}
devt=`cat /sys/block/$devname/dev`
pid=""
runtime=2

clean_up_test() {
        pill -9 $pid
        echo clear > /sys/block/md0/md/array_state
}

trap 'clean_up_test' EXIT

add_by_sysfs() {
        while true; do
                echo $devt > /sys/block/md0/md/new_dev
        done
}

remove_by_sysfs(){
        while true; do
                echo remove > /sys/block/md0/md/dev-${devname}/state
        done
}

echo md0 > /sys/module/md_mod/parameters/new_array || die "create md0 failed"

add_by_sysfs &
pid="$pid $!"

remove_by_sysfs &
pid="$pid $!"

sleep $runtime
exit 0

Test cmd:

./test --save-logs --logdir=/tmp/ --keep-going --dev=loop --tests=23rdev-lifetime

Test result:

general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6bcb: 0000 [#4] PREEMPT SMP
CPU: 0 PID: 1292 Comm: test Tainted: G      D W          6.5.0-rc2-00121-g01e55c376936 #562
RIP: 0010:md_wakeup_thread+0x9e/0x320 [md_mod]
Call Trace:
 <TASK>
 mddev_unlock+0x1b6/0x310 [md_mod]
 rdev_attr_store+0xec/0x190 [md_mod]
 sysfs_kf_write+0x52/0x70
 kernfs_fop_write_iter+0x19a/0x2a0
 vfs_write+0x3b5/0x770
 ksys_write+0x74/0x150
 __x64_sys_write+0x22/0x30
 do_syscall_64+0x40/0x90
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fix this problem by don't dereference mddev after export_rdev().

The Linux kernel CVE team has assigned CVE-2023-53665 to this issue.


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

	Issue introduced in 6.5 with commit 3ce94ce5d05ae89190a23f6187f64d8f4b2d3782 and fixed in 6.5.5 with commit ad430ad0669d2757377373390d68e1454fc7a344
	Issue introduced in 6.5 with commit 3ce94ce5d05ae89190a23f6187f64d8f4b2d3782 and fixed in 6.6 with commit 7deac114be5fb25a4e865212ed0feaf5f85f2a28

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-2023-53665
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/ad430ad0669d2757377373390d68e1454fc7a344
	https://git.kernel.org/stable/c/7deac114be5fb25a4e865212ed0feaf5f85f2a28