linux-cve-announce - CVE-2025-68368: md: init bioset in mddev

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Message-ID: <2025122400-CVE-2025-68368-4e1b@gregkh>
Date: Wed, 24 Dec 2025 11:35:13 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68368: md: init bioset in mddev_init

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

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

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

md: init bioset in mddev_init

IO operations may be needed before md_run(), such as updating metadata
after writing sysfs. Without bioset, this triggers a NULL pointer
dereference as below:

 BUG: kernel NULL pointer dereference, address: 0000000000000020
 Call Trace:
  md_update_sb+0x658/0xe00
  new_level_store+0xc5/0x120
  md_attr_store+0xc9/0x1e0
  sysfs_kf_write+0x6f/0xa0
  kernfs_fop_write_iter+0x141/0x2a0
  vfs_write+0x1fc/0x5a0
  ksys_write+0x79/0x180
  __x64_sys_write+0x1d/0x30
  x64_sys_call+0x2818/0x2880
  do_syscall_64+0xa9/0x580
  entry_SYSCALL_64_after_hwframe+0x4b/0x53

Reproducer
```
  mdadm -CR /dev/md0 -l1 -n2 /dev/sd[cd]
  echo inactive > /sys/block/md0/md/array_state
  echo 10 > /sys/block/md0/md/new_level
```

mddev_init() can only be called once per mddev, no need to test if bioset
has been initialized anymore.

The Linux kernel CVE team has assigned CVE-2025-68368 to this issue.


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

	Issue introduced in 6.12 with commit d981ed8419303ed12351eea8541ad6cb76455fe3 and fixed in 6.18.2 with commit 9d37fe37dfa0833a8768740f0575e0ffd793cb4a
	Issue introduced in 6.12 with commit d981ed8419303ed12351eea8541ad6cb76455fe3 and fixed in 6.19-rc1 with commit 381a3ce1c0ffed647c9b913e142b099c7e9d5afc

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-2025-68368
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/9d37fe37dfa0833a8768740f0575e0ffd793cb4a
	https://git.kernel.org/stable/c/381a3ce1c0ffed647c9b913e142b099c7e9d5afc