linux-cve-announce - CVE-2022-50373: fs: dlm: fix race in lowcomms

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Message-ID: <2025091717-CVE-2022-50373-ce58@gregkh>
Date: Wed, 17 Sep 2025 16:56:32 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50373: fs: dlm: fix race in lowcomms

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

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

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

fs: dlm: fix race in lowcomms

This patch fixes a race between queue_work() in
_dlm_lowcomms_commit_msg() and srcu_read_unlock(). The queue_work() can
take the final reference of a dlm_msg and so msg->idx can contain
garbage which is signaled by the following warning:

[  676.237050] ------------[ cut here ]------------
[  676.237052] WARNING: CPU: 0 PID: 1060 at include/linux/srcu.h:189 dlm_lowcomms_commit_msg+0x41/0x50
[  676.238945] Modules linked in: dlm_locktorture torture rpcsec_gss_krb5 intel_rapl_msr intel_rapl_common iTCO_wdt iTCO_vendor_support qxl kvm_intel drm_ttm_helper vmw_vsock_virtio_transport kvm vmw_vsock_virtio_transport_common ttm irqbypass crc32_pclmul joydev crc32c_intel serio_raw drm_kms_helper vsock virtio_scsi virtio_console virtio_balloon snd_pcm drm syscopyarea sysfillrect sysimgblt snd_timer fb_sys_fops i2c_i801 lpc_ich snd i2c_smbus soundcore pcspkr
[  676.244227] CPU: 0 PID: 1060 Comm: lock_torture_wr Not tainted 5.19.0-rc3+ #1546
[  676.245216] Hardware name: Red Hat KVM/RHEL-AV, BIOS 1.16.0-2.module+el8.7.0+15506+033991b0 04/01/2014
[  676.246460] RIP: 0010:dlm_lowcomms_commit_msg+0x41/0x50
[  676.247132] Code: fe ff ff ff 75 24 48 c7 c6 bd 0f 49 bb 48 c7 c7 38 7c 01 bd e8 00 e7 ca ff 89 de 48 c7 c7 60 78 01 bd e8 42 3d cd ff 5b 5d c3 <0f> 0b eb d8 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48
[  676.249253] RSP: 0018:ffffa401c18ffc68 EFLAGS: 00010282
[  676.249855] RAX: 0000000000000001 RBX: 00000000ffff8b76 RCX: 0000000000000006
[  676.250713] RDX: 0000000000000000 RSI: ffffffffbccf3a10 RDI: ffffffffbcc7b62e
[  676.251610] RBP: ffffa401c18ffc70 R08: 0000000000000001 R09: 0000000000000001
[  676.252481] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000005
[  676.253421] R13: ffff8b76786ec370 R14: ffff8b76786ec370 R15: ffff8b76786ec480
[  676.254257] FS:  0000000000000000(0000) GS:ffff8b7777800000(0000) knlGS:0000000000000000
[  676.255239] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  676.255897] CR2: 00005590205d88b8 CR3: 000000017656c003 CR4: 0000000000770ee0
[  676.256734] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  676.257567] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  676.258397] PKRU: 55555554
[  676.258729] Call Trace:
[  676.259063]  <TASK>
[  676.259354]  dlm_midcomms_commit_mhandle+0xcc/0x110
[  676.259964]  queue_bast+0x8b/0xb0
[  676.260423]  grant_pending_locks+0x166/0x1b0
[  676.261007]  _unlock_lock+0x75/0x90
[  676.261469]  unlock_lock.isra.57+0x62/0xa0
[  676.262009]  dlm_unlock+0x21e/0x330
[  676.262457]  ? lock_torture_stats+0x80/0x80 [dlm_locktorture]
[  676.263183]  torture_unlock+0x5a/0x90 [dlm_locktorture]
[  676.263815]  ? preempt_count_sub+0xba/0x100
[  676.264361]  ? complete+0x1d/0x60
[  676.264777]  lock_torture_writer+0xb8/0x150 [dlm_locktorture]
[  676.265555]  kthread+0x10a/0x130
[  676.266007]  ? kthread_complete_and_exit+0x20/0x20
[  676.266616]  ret_from_fork+0x22/0x30
[  676.267097]  </TASK>
[  676.267381] irq event stamp: 9579855
[  676.267824] hardirqs last  enabled at (9579863): [<ffffffffbb14e6f8>] __up_console_sem+0x58/0x60
[  676.268896] hardirqs last disabled at (9579872): [<ffffffffbb14e6dd>] __up_console_sem+0x3d/0x60
[  676.270008] softirqs last  enabled at (9579798): [<ffffffffbc200349>] __do_softirq+0x349/0x4c7
[  676.271438] softirqs last disabled at (9579897): [<ffffffffbb0d54c0>] irq_exit_rcu+0xb0/0xf0
[  676.272796] ---[ end trace 0000000000000000 ]---

I reproduced this warning with dlm_locktorture test which is currently
not upstream. However this patch fix the issue by make a additional
refcount between dlm_lowcomms_new_msg() and dlm_lowcomms_commit_msg().
In case of the race the kref_put() in dlm_lowcomms_commit_msg() will be
the final put.

The Linux kernel CVE team has assigned CVE-2022-50373 to this issue.


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

	Fixed in 5.15.75 with commit 27d3e646dd83bafd7094890462eebfce3ac31e4a
	Fixed in 5.19.17 with commit eb97e60a9eae632ff9104a580dbc4fdc58dc23cb
	Fixed in 6.0.3 with commit de7fdff754bb4d01e38e19964c309b6df6a79472
	Fixed in 6.1 with commit 30ea3257e8766027c4d8d609dcbd256ff9a76073

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-2022-50373
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:
	fs/dlm/lowcomms.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/27d3e646dd83bafd7094890462eebfce3ac31e4a
	https://git.kernel.org/stable/c/eb97e60a9eae632ff9104a580dbc4fdc58dc23cb
	https://git.kernel.org/stable/c/de7fdff754bb4d01e38e19964c309b6df6a79472
	https://git.kernel.org/stable/c/30ea3257e8766027c4d8d609dcbd256ff9a76073