Message-ID: <2025100710-CVE-2023-53621-b6f9@gregkh>
Date: Tue,  7 Oct 2025 17:19:26 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53621: memcontrol: ensure memcg acquired by id is properly set up

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

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

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

memcontrol: ensure memcg acquired by id is properly set up

In the eviction recency check, we attempt to retrieve the memcg to which
the folio belonged when it was evicted, by the memcg id stored in the
shadow entry.  However, there is a chance that the retrieved memcg is not
the original memcg that has been killed, but a new one which happens to
have the same id.

This is a somewhat unfortunate, but acceptable and rare inaccuracy in the
heuristics.  However, if we retrieve this new memcg between its allocation
and when it is properly attached to the memcg hierarchy, we could run into
the following NULL pointer exception during the memcg hierarchy traversal
done in mem_cgroup_get_nr_swap_pages():

[ 155757.793456] BUG: kernel NULL pointer dereference, address: 00000000000000c0
[ 155757.807568] #PF: supervisor read access in kernel mode
[ 155757.818024] #PF: error_code(0x0000) - not-present page
[ 155757.828482] PGD 401f77067 P4D 401f77067 PUD 401f76067 PMD 0
[ 155757.839985] Oops: 0000 [#1] SMP
[ 155757.887870] RIP: 0010:mem_cgroup_get_nr_swap_pages+0x3d/0xb0
[ 155757.899377] Code: 29 19 4a 02 48 39 f9 74 63 48 8b 97 c0 00 00 00 48 8b b7 58 02 00 00 48 2b b7 c0 01 00 00 48 39 f0 48 0f 4d c6 48 39 d1 74 42 <48> 8b b2 c0 00 00 00 48 8b ba 58 02 00 00 48 2b ba c0 01 00 00 48
[ 155757.937125] RSP: 0018:ffffc9002ecdfbc8 EFLAGS: 00010286
[ 155757.947755] RAX: 00000000003a3b1c RBX: 000007ffffffffff RCX: ffff888280183000
[ 155757.962202] RDX: 0000000000000000 RSI: 0007ffffffffffff RDI: ffff888bbc2d1000
[ 155757.976648] RBP: 0000000000000001 R08: 000000000000000b R09: ffff888ad9cedba0
[ 155757.991094] R10: ffffea0039c07900 R11: 0000000000000010 R12: ffff888b23a7b000
[ 155758.005540] R13: 0000000000000000 R14: ffff888bbc2d1000 R15: 000007ffffc71354
[ 155758.019991] FS:  00007f6234c68640(0000) GS:ffff88903f9c0000(0000) knlGS:0000000000000000
[ 155758.036356] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 155758.048023] CR2: 00000000000000c0 CR3: 0000000a83eb8004 CR4: 00000000007706e0
[ 155758.062473] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 155758.076924] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 155758.091376] PKRU: 55555554
[ 155758.096957] Call Trace:
[ 155758.102016]  <TASK>
[ 155758.106502]  ? __die+0x78/0xc0
[ 155758.112793]  ? page_fault_oops+0x286/0x380
[ 155758.121175]  ? exc_page_fault+0x5d/0x110
[ 155758.129209]  ? asm_exc_page_fault+0x22/0x30
[ 155758.137763]  ? mem_cgroup_get_nr_swap_pages+0x3d/0xb0
[ 155758.148060]  workingset_test_recent+0xda/0x1b0
[ 155758.157133]  workingset_refault+0xca/0x1e0
[ 155758.165508]  filemap_add_folio+0x4d/0x70
[ 155758.173538]  page_cache_ra_unbounded+0xed/0x190
[ 155758.182919]  page_cache_sync_ra+0xd6/0x1e0
[ 155758.191738]  filemap_read+0x68d/0xdf0
[ 155758.199495]  ? mlx5e_napi_poll+0x123/0x940
[ 155758.207981]  ? __napi_schedule+0x55/0x90
[ 155758.216095]  __x64_sys_pread64+0x1d6/0x2c0
[ 155758.224601]  do_syscall_64+0x3d/0x80
[ 155758.232058]  entry_SYSCALL_64_after_hwframe+0x46/0xb0
[ 155758.242473] RIP: 0033:0x7f62c29153b5
[ 155758.249938] Code: e8 48 89 75 f0 89 7d f8 48 89 4d e0 e8 b4 e6 f7 ff 41 89 c0 4c 8b 55 e0 48 8b 55 e8 48 8b 75 f0 8b 7d f8 b8 11 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 33 44 89 c7 48 89 45 f8 e8 e7 e6 f7 ff 48 8b
[ 155758.288005] RSP: 002b:00007f6234c5ffd0 EFLAGS: 00000293 ORIG_RAX: 0000000000000011
[ 155758.303474] RAX: ffffffffffffffda RBX: 00007f628c4e70c0 RCX: 00007f62c29153b5
[ 155758.318075] RDX: 000000000003c041 RSI: 00007f61d2986000 RDI: 0000000000000076
[ 155758.332678] RBP: 00007f6234c5fff0 R08: 0000000000000000 R09: 0000000064d5230c
[ 155758.347452] R10: 000000000027d450 R11: 0000000000000293 R12: 000000000003c041
[ 155758.362044] R13: 00007f61d2986000 R14: 00007f629e11b060 R15: 000000000027d450
[ 155758.376661]  </TASK>

This patch fixes the issue by moving the memcg's id publication from the
alloc stage to online stage, ensuring that any memcg acquired via id must
be connected to the memcg tree.

The Linux kernel CVE team has assigned CVE-2023-53621 to this issue.


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

	Issue introduced in 6.3 with commit f78dfc7b77d5c3527d0f895bef693f711802de5a and fixed in 6.5.4 with commit b9d30c38ee859d833a51131b5b4b864c7a6219d0
	Issue introduced in 6.3 with commit f78dfc7b77d5c3527d0f895bef693f711802de5a and fixed in 6.6 with commit 6f0df8e16eb543167f2929cb756e695709a3551d

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-2023-53621
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/memcontrol.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/b9d30c38ee859d833a51131b5b4b864c7a6219d0
	https://git.kernel.org/stable/c/6f0df8e16eb543167f2929cb756e695709a3551d

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