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Message-ID: <2025123019-CVE-2023-54165-1362@gregkh>
Date: Tue, 30 Dec 2025 13:09:33 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-54165: zsmalloc: move LRU update from zs_map_object() to zs_malloc()
From: Greg Kroah-Hartman <gregkh@...nel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
zsmalloc: move LRU update from zs_map_object() to zs_malloc()
Under memory pressure, we sometimes observe the following crash:
[ 5694.832838] ------------[ cut here ]------------
[ 5694.842093] list_del corruption, ffff888014b6a448->next is LIST_POISON1 (dead000000000100)
[ 5694.858677] WARNING: CPU: 33 PID: 418824 at lib/list_debug.c:47 __list_del_entry_valid+0x42/0x80
[ 5694.961820] CPU: 33 PID: 418824 Comm: fuse_counters.s Kdump: loaded Tainted: G S 5.19.0-0_fbk3_rc3_hoangnhatpzsdynshrv41_10870_g85a9558a25de #1
[ 5694.990194] Hardware name: Wiwynn Twin Lakes MP/Twin Lakes Passive MP, BIOS YMM16 05/24/2021
[ 5695.007072] RIP: 0010:__list_del_entry_valid+0x42/0x80
[ 5695.017351] Code: 08 48 83 c2 22 48 39 d0 74 24 48 8b 10 48 39 f2 75 2c 48 8b 51 08 b0 01 48 39 f2 75 34 c3 48 c7 c7 55 d7 78 82 e8 4e 45 3b 00 <0f> 0b eb 31 48 c7 c7 27 a8 70 82 e8 3e 45 3b 00 0f 0b eb 21 48 c7
[ 5695.054919] RSP: 0018:ffffc90027aef4f0 EFLAGS: 00010246
[ 5695.065366] RAX: 41fe484987275300 RBX: ffff888008988180 RCX: 0000000000000000
[ 5695.079636] RDX: ffff88886006c280 RSI: ffff888860060480 RDI: ffff888860060480
[ 5695.093904] RBP: 0000000000000002 R08: 0000000000000000 R09: ffffc90027aef370
[ 5695.108175] R10: 0000000000000000 R11: ffffffff82fdf1c0 R12: 0000000010000002
[ 5695.122447] R13: ffff888014b6a448 R14: ffff888014b6a420 R15: 00000000138dc240
[ 5695.136717] FS: 00007f23a7d3f740(0000) GS:ffff888860040000(0000) knlGS:0000000000000000
[ 5695.152899] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 5695.164388] CR2: 0000560ceaab6ac0 CR3: 000000001c06c001 CR4: 00000000007706e0
[ 5695.178659] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 5695.192927] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 5695.207197] PKRU: 55555554
[ 5695.212602] Call Trace:
[ 5695.217486] <TASK>
[ 5695.221674] zs_map_object+0x91/0x270
[ 5695.229000] zswap_frontswap_store+0x33d/0x870
[ 5695.237885] ? do_raw_spin_lock+0x5d/0xa0
[ 5695.245899] __frontswap_store+0x51/0xb0
[ 5695.253742] swap_writepage+0x3c/0x60
[ 5695.261063] shrink_page_list+0x738/0x1230
[ 5695.269255] shrink_lruvec+0x5ec/0xcd0
[ 5695.276749] ? shrink_slab+0x187/0x5f0
[ 5695.284240] ? mem_cgroup_iter+0x6e/0x120
[ 5695.292255] shrink_node+0x293/0x7b0
[ 5695.299402] do_try_to_free_pages+0xea/0x550
[ 5695.307940] try_to_free_pages+0x19a/0x490
[ 5695.316126] __folio_alloc+0x19ff/0x3e40
[ 5695.323971] ? __filemap_get_folio+0x8a/0x4e0
[ 5695.332681] ? walk_component+0x2a8/0xb50
[ 5695.340697] ? generic_permission+0xda/0x2a0
[ 5695.349231] ? __filemap_get_folio+0x8a/0x4e0
[ 5695.357940] ? walk_component+0x2a8/0xb50
[ 5695.365955] vma_alloc_folio+0x10e/0x570
[ 5695.373796] ? walk_component+0x52/0xb50
[ 5695.381634] wp_page_copy+0x38c/0xc10
[ 5695.388953] ? filename_lookup+0x378/0xbc0
[ 5695.397140] handle_mm_fault+0x87f/0x1800
[ 5695.405157] do_user_addr_fault+0x1bd/0x570
[ 5695.413520] exc_page_fault+0x5d/0x110
[ 5695.421017] asm_exc_page_fault+0x22/0x30
After some investigation, I have found the following issue: unlike other
zswap backends, zsmalloc performs the LRU list update at the object
mapping time, rather than when the slot for the object is allocated.
This deviation was discussed and agreed upon during the review process
of the zsmalloc writeback patch series:
https://lore.kernel.org/lkml/Y3flcAXNxxrvy3ZH@cmpxchg.org/
Unfortunately, this introduces a subtle bug that occurs when there is a
concurrent store and reclaim, which interleave as follows:
zswap_frontswap_store() shrink_worker()
zs_malloc() zs_zpool_shrink()
spin_lock(&pool->lock) zs_reclaim_page()
zspage = find_get_zspage()
spin_unlock(&pool->lock)
spin_lock(&pool->lock)
zspage = list_first_entry(&pool->lru)
list_del(&zspage->lru)
zspage->lru.next = LIST_POISON1
zspage->lru.prev = LIST_POISON2
spin_unlock(&pool->lock)
zs_map_object()
spin_lock(&pool->lock)
if (!list_empty(&zspage->lru))
list_del(&zspage->lru)
CHECK_DATA_CORRUPTION(next == LIST_POISON1) /* BOOM */
With the current upstream code, this issue rarely happens. zswap only
triggers writeback when the pool is already full, at which point all
further store attempts are short-circuited. This creates an implicit
pseudo-serialization between reclaim and store. I am working on a new
zswap shrinking mechanism, which makes interleaving reclaim and store
more likely, exposing this bug.
zbud and z3fold do not have this problem, because they perform the LRU
list update in the alloc function, while still holding the pool's lock.
This patch fixes the aforementioned bug by moving the LRU update back to
zs_malloc(), analogous to zbud and z3fold.
The Linux kernel CVE team has assigned CVE-2023-54165 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.2 with commit 64f768c6b32e1957e2b65b70e97cb4cb62344bc4 and fixed in 6.3.5 with commit e95adf7486f2cb5f1bb303113ca30460951923e9
Issue introduced in 6.2 with commit 64f768c6b32e1957e2b65b70e97cb4cb62344bc4 and fixed in 6.4 with commit d461aac924b937bcb4fd0ca1242b3ef6868ecddd
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-2023-54165
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/zsmalloc.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/e95adf7486f2cb5f1bb303113ca30460951923e9
https://git.kernel.org/stable/c/d461aac924b937bcb4fd0ca1242b3ef6868ecddd
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