Message-ID: <2025100710-CVE-2023-53623-2687@gregkh>
Date: Tue,  7 Oct 2025 17:19:28 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53623: mm/swap: fix swap_info_struct race between swapoff and get_swap_pages()

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

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

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

mm/swap: fix swap_info_struct race between swapoff and get_swap_pages()

The si->lock must be held when deleting the si from the available list. 
Otherwise, another thread can re-add the si to the available list, which
can lead to memory corruption.  The only place we have found where this
happens is in the swapoff path.  This case can be described as below:

core 0                       core 1
swapoff

del_from_avail_list(si)      waiting

try lock si->lock            acquire swap_avail_lock
                             and re-add si into
                             swap_avail_head

acquire si->lock but missing si already being added again, and continuing
to clear SWP_WRITEOK, etc.

It can be easily found that a massive warning messages can be triggered
inside get_swap_pages() by some special cases, for example, we call
madvise(MADV_PAGEOUT) on blocks of touched memory concurrently, meanwhile,
run much swapon-swapoff operations (e.g.  stress-ng-swap).

However, in the worst case, panic can be caused by the above scene.  In
swapoff(), the memory used by si could be kept in swap_info[] after
turning off a swap.  This means memory corruption will not be caused
immediately until allocated and reset for a new swap in the swapon path. 
A panic message caused: (with CONFIG_PLIST_DEBUG enabled)

------------[ cut here ]------------
top: 00000000e58a3003, n: 0000000013e75cda, p: 000000008cd4451a
prev: 0000000035b1e58a, n: 000000008cd4451a, p: 000000002150ee8d
next: 000000008cd4451a, n: 000000008cd4451a, p: 000000008cd4451a
WARNING: CPU: 21 PID: 1843 at lib/plist.c:60 plist_check_prev_next_node+0x50/0x70
Modules linked in: rfkill(E) crct10dif_ce(E)...
CPU: 21 PID: 1843 Comm: stress-ng Kdump: ... 5.10.134+
Hardware name: Alibaba Cloud ECS, BIOS 0.0.0 02/06/2015
pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--)
pc : plist_check_prev_next_node+0x50/0x70
lr : plist_check_prev_next_node+0x50/0x70
sp : ffff0018009d3c30
x29: ffff0018009d3c40 x28: ffff800011b32a98
x27: 0000000000000000 x26: ffff001803908000
x25: ffff8000128ea088 x24: ffff800011b32a48
x23: 0000000000000028 x22: ffff001800875c00
x21: ffff800010f9e520 x20: ffff001800875c00
x19: ffff001800fdc6e0 x18: 0000000000000030
x17: 0000000000000000 x16: 0000000000000000
x15: 0736076307640766 x14: 0730073007380731
x13: 0736076307640766 x12: 0730073007380731
x11: 000000000004058d x10: 0000000085a85b76
x9 : ffff8000101436e4 x8 : ffff800011c8ce08
x7 : 0000000000000000 x6 : 0000000000000001
x5 : ffff0017df9ed338 x4 : 0000000000000001
x3 : ffff8017ce62a000 x2 : ffff0017df9ed340
x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
 plist_check_prev_next_node+0x50/0x70
 plist_check_head+0x80/0xf0
 plist_add+0x28/0x140
 add_to_avail_list+0x9c/0xf0
 _enable_swap_info+0x78/0xb4
 __do_sys_swapon+0x918/0xa10
 __arm64_sys_swapon+0x20/0x30
 el0_svc_common+0x8c/0x220
 do_el0_svc+0x2c/0x90
 el0_svc+0x1c/0x30
 el0_sync_handler+0xa8/0xb0
 el0_sync+0x148/0x180
irq event stamp: 2082270

Now, si->lock locked before calling 'del_from_avail_list()' to make sure
other thread see the si had been deleted and SWP_WRITEOK cleared together,
will not reinsert again.

This problem exists in versions after stable 5.10.y.

The Linux kernel CVE team has assigned CVE-2023-53623 to this issue.


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

	Issue introduced in 4.14 with commit a2468cc9bfdff6139f59ca896671e5819ff5f94a and fixed in 4.14.313 with commit 111a79d9b92f0a679fe300ccd3119ae9741f3d54
	Issue introduced in 4.14 with commit a2468cc9bfdff6139f59ca896671e5819ff5f94a and fixed in 4.19.281 with commit a55f268abdb74ac5633b75a09fefb58458e9d2a2
	Issue introduced in 4.14 with commit a2468cc9bfdff6139f59ca896671e5819ff5f94a and fixed in 5.4.241 with commit e7bba7ddb4318d5ea939c8db747c2c2780ab66f4
	Issue introduced in 4.14 with commit a2468cc9bfdff6139f59ca896671e5819ff5f94a and fixed in 5.10.178 with commit ea8c42b3b6d95ced3a4f555f04686d00ef0bb206
	Issue introduced in 4.14 with commit a2468cc9bfdff6139f59ca896671e5819ff5f94a and fixed in 5.15.107 with commit 4bdf1514b4268d29360ba9e43becdd49955bc7ae
	Issue introduced in 4.14 with commit a2468cc9bfdff6139f59ca896671e5819ff5f94a and fixed in 6.1.24 with commit 85cc118ce6f1a627901b6db50c9d01f2ad78cdbf
	Issue introduced in 4.14 with commit a2468cc9bfdff6139f59ca896671e5819ff5f94a and fixed in 6.2.11 with commit b9927d3a60ca9ed35625470888629c074e687ba0
	Issue introduced in 4.14 with commit a2468cc9bfdff6139f59ca896671e5819ff5f94a and fixed in 6.3 with commit 6fe7d6b992113719e96744d974212df3fcddc76c

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-2023-53623
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:
	mm/swapfile.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/111a79d9b92f0a679fe300ccd3119ae9741f3d54
	https://git.kernel.org/stable/c/a55f268abdb74ac5633b75a09fefb58458e9d2a2
	https://git.kernel.org/stable/c/e7bba7ddb4318d5ea939c8db747c2c2780ab66f4
	https://git.kernel.org/stable/c/ea8c42b3b6d95ced3a4f555f04686d00ef0bb206
	https://git.kernel.org/stable/c/4bdf1514b4268d29360ba9e43becdd49955bc7ae
	https://git.kernel.org/stable/c/85cc118ce6f1a627901b6db50c9d01f2ad78cdbf
	https://git.kernel.org/stable/c/b9927d3a60ca9ed35625470888629c074e687ba0
	https://git.kernel.org/stable/c/6fe7d6b992113719e96744d974212df3fcddc76c

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