linux-cve-announce - CVE-2022-50697: mrp: introduce active flags to prevent UAF when applicant uninit

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Message-ID: <2025122415-CVE-2022-50697-6281@gregkh>
Date: Wed, 24 Dec 2025 11:56:14 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50697: mrp: introduce active flags to prevent UAF when applicant uninit

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

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

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

mrp: introduce active flags to prevent UAF when applicant uninit

The caller of del_timer_sync must prevent restarting of the timer, If
we have no this synchronization, there is a small probability that the
cancellation will not be successful.

And syzbot report the fellowing crash:
==================================================================
BUG: KASAN: use-after-free in hlist_add_head include/linux/list.h:929 [inline]
BUG: KASAN: use-after-free in enqueue_timer+0x18/0xa4 kernel/time/timer.c:605
Write at addr f9ff000024df6058 by task syz-fuzzer/2256
Pointer tag: [f9], memory tag: [fe]

CPU: 1 PID: 2256 Comm: syz-fuzzer Not tainted 6.1.0-rc5-syzkaller-00008-
ge01d50cbd6ee #0
Hardware name: linux,dummy-virt (DT)
Call trace:
 dump_backtrace.part.0+0xe0/0xf0 arch/arm64/kernel/stacktrace.c:156
 dump_backtrace arch/arm64/kernel/stacktrace.c:162 [inline]
 show_stack+0x18/0x40 arch/arm64/kernel/stacktrace.c:163
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x68/0x84 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:284 [inline]
 print_report+0x1a8/0x4a0 mm/kasan/report.c:395
 kasan_report+0x94/0xb4 mm/kasan/report.c:495
 __do_kernel_fault+0x164/0x1e0 arch/arm64/mm/fault.c:320
 do_bad_area arch/arm64/mm/fault.c:473 [inline]
 do_tag_check_fault+0x78/0x8c arch/arm64/mm/fault.c:749
 do_mem_abort+0x44/0x94 arch/arm64/mm/fault.c:825
 el1_abort+0x40/0x60 arch/arm64/kernel/entry-common.c:367
 el1h_64_sync_handler+0xd8/0xe4 arch/arm64/kernel/entry-common.c:427
 el1h_64_sync+0x64/0x68 arch/arm64/kernel/entry.S:576
 hlist_add_head include/linux/list.h:929 [inline]
 enqueue_timer+0x18/0xa4 kernel/time/timer.c:605
 mod_timer+0x14/0x20 kernel/time/timer.c:1161
 mrp_periodic_timer_arm net/802/mrp.c:614 [inline]
 mrp_periodic_timer+0xa0/0xc0 net/802/mrp.c:627
 call_timer_fn.constprop.0+0x24/0x80 kernel/time/timer.c:1474
 expire_timers+0x98/0xc4 kernel/time/timer.c:1519

To fix it, we can introduce a new active flags to make sure the timer will
not restart.

The Linux kernel CVE team has assigned CVE-2022-50697 to this issue.


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

	Fixed in 4.9.337 with commit 98f53e591940e4c3818be358c5dc684d5b30cb56
	Fixed in 4.14.303 with commit aacffc1a8dbf67c5463cb4f67b37143c01ca6fa9
	Fixed in 4.19.270 with commit 78d48bc41f7726113c9f114268d3ab11212814da
	Fixed in 5.4.229 with commit aadb1507a77b060c529edfeaf67f803e31461f24
	Fixed in 5.10.163 with commit 755eb0879224ffc2a43de724554aeaf0e51e5a64
	Fixed in 5.15.86 with commit 5d5a481a7fd0234f617535dc464ea010804a1129
	Fixed in 6.0.16 with commit 1a185fe83c2a60c1e3596fb9d82dbeb148dc09c6
	Fixed in 6.1.2 with commit 563e45fd5046045cc194af3ba17f5423e1c98170
	Fixed in 6.2 with commit ab0377803dafc58f1e22296708c1c28e309414d6

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-2022-50697
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:
	include/net/mrp.h
	net/802/mrp.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/98f53e591940e4c3818be358c5dc684d5b30cb56
	https://git.kernel.org/stable/c/aacffc1a8dbf67c5463cb4f67b37143c01ca6fa9
	https://git.kernel.org/stable/c/78d48bc41f7726113c9f114268d3ab11212814da
	https://git.kernel.org/stable/c/aadb1507a77b060c529edfeaf67f803e31461f24
	https://git.kernel.org/stable/c/755eb0879224ffc2a43de724554aeaf0e51e5a64
	https://git.kernel.org/stable/c/5d5a481a7fd0234f617535dc464ea010804a1129
	https://git.kernel.org/stable/c/1a185fe83c2a60c1e3596fb9d82dbeb148dc09c6
	https://git.kernel.org/stable/c/563e45fd5046045cc194af3ba17f5423e1c98170
	https://git.kernel.org/stable/c/ab0377803dafc58f1e22296708c1c28e309414d6