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Message-ID: <2025070937-CVE-2025-38263-cc93@gregkh>
Date: Wed, 9 Jul 2025 12:42:55 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38263: bcache: fix NULL pointer in cache_set_flush()
From: Greg Kroah-Hartman <gregkh@...nel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
bcache: fix NULL pointer in cache_set_flush()
1. LINE#1794 - LINE#1887 is some codes about function of
bch_cache_set_alloc().
2. LINE#2078 - LINE#2142 is some codes about function of
register_cache_set().
3. register_cache_set() will call bch_cache_set_alloc() in LINE#2098.
1794 struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
1795 {
...
1860 if (!(c->devices = kcalloc(c->nr_uuids, sizeof(void *), GFP_KERNEL)) ||
1861 mempool_init_slab_pool(&c->search, 32, bch_search_cache) ||
1862 mempool_init_kmalloc_pool(&c->bio_meta, 2,
1863 sizeof(struct bbio) + sizeof(struct bio_vec) *
1864 bucket_pages(c)) ||
1865 mempool_init_kmalloc_pool(&c->fill_iter, 1, iter_size) ||
1866 bioset_init(&c->bio_split, 4, offsetof(struct bbio, bio),
1867 BIOSET_NEED_BVECS|BIOSET_NEED_RESCUER) ||
1868 !(c->uuids = alloc_bucket_pages(GFP_KERNEL, c)) ||
1869 !(c->moving_gc_wq = alloc_workqueue("bcache_gc",
1870 WQ_MEM_RECLAIM, 0)) ||
1871 bch_journal_alloc(c) ||
1872 bch_btree_cache_alloc(c) ||
1873 bch_open_buckets_alloc(c) ||
1874 bch_bset_sort_state_init(&c->sort, ilog2(c->btree_pages)))
1875 goto err;
^^^^^^^^
1876
...
1883 return c;
1884 err:
1885 bch_cache_set_unregister(c);
^^^^^^^^^^^^^^^^^^^^^^^^^^^
1886 return NULL;
1887 }
...
2078 static const char *register_cache_set(struct cache *ca)
2079 {
...
2098 c = bch_cache_set_alloc(&ca->sb);
2099 if (!c)
2100 return err;
^^^^^^^^^^
...
2128 ca->set = c;
2129 ca->set->cache[ca->sb.nr_this_dev] = ca;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
2138 return NULL;
2139 err:
2140 bch_cache_set_unregister(c);
2141 return err;
2142 }
(1) If LINE#1860 - LINE#1874 is true, then do 'goto err'(LINE#1875) and
call bch_cache_set_unregister()(LINE#1885).
(2) As (1) return NULL(LINE#1886), LINE#2098 - LINE#2100 would return.
(3) As (2) has returned, LINE#2128 - LINE#2129 would do *not* give the
value to c->cache[], it means that c->cache[] is NULL.
LINE#1624 - LINE#1665 is some codes about function of cache_set_flush().
As (1), in LINE#1885 call
bch_cache_set_unregister()
---> bch_cache_set_stop()
---> closure_queue()
-.-> cache_set_flush() (as below LINE#1624)
1624 static void cache_set_flush(struct closure *cl)
1625 {
...
1654 for_each_cache(ca, c, i)
1655 if (ca->alloc_thread)
^^
1656 kthread_stop(ca->alloc_thread);
...
1665 }
(4) In LINE#1655 ca is NULL(see (3)) in cache_set_flush() then the
kernel crash occurred as below:
[ 846.712887] bcache: register_cache() error drbd6: cannot allocate memory
[ 846.713242] bcache: register_bcache() error : failed to register device
[ 846.713336] bcache: cache_set_free() Cache set 2f84bdc1-498a-4f2f-98a7-01946bf54287 unregistered
[ 846.713768] BUG: unable to handle kernel NULL pointer dereference at 00000000000009f8
[ 846.714790] PGD 0 P4D 0
[ 846.715129] Oops: 0000 [#1] SMP PTI
[ 846.715472] CPU: 19 PID: 5057 Comm: kworker/19:16 Kdump: loaded Tainted: G OE --------- - - 4.18.0-147.5.1.el8_1.5es.3.x86_64 #1
[ 846.716082] Hardware name: ESPAN GI-25212/X11DPL-i, BIOS 2.1 06/15/2018
[ 846.716451] Workqueue: events cache_set_flush [bcache]
[ 846.716808] RIP: 0010:cache_set_flush+0xc9/0x1b0 [bcache]
[ 846.717155] Code: 00 4c 89 a5 b0 03 00 00 48 8b 85 68 f6 ff ff a8 08 0f 84 88 00 00 00 31 db 66 83 bd 3c f7 ff ff 00 48 8b 85 48 ff ff ff 74 28 <48> 8b b8 f8 09 00 00 48 85 ff 74 05 e8 b6 58 a2 e1 0f b7 95 3c f7
[ 846.718026] RSP: 0018:ffffb56dcf85fe70 EFLAGS: 00010202
[ 846.718372] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[ 846.718725] RDX: 0000000000000001 RSI: 0000000040000001 RDI: 0000000000000000
[ 846.719076] RBP: ffffa0ccc0f20df8 R08: ffffa0ce1fedb118 R09: 000073746e657665
[ 846.719428] R10: 8080808080808080 R11: 0000000000000000 R12: ffffa0ce1fee8700
[ 846.719779] R13: ffffa0ccc0f211a8 R14: ffffa0cd1b902840 R15: ffffa0ccc0f20e00
[ 846.720132] FS: 0000000000000000(0000) GS:ffffa0ce1fec0000(0000) knlGS:0000000000000000
[ 846.720726] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 846.721073] CR2: 00000000000009f8 CR3: 00000008ba00a005 CR4: 00000000007606e0
[ 846.721426] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 846.721778] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 846.722131] PKRU: 55555554
[ 846.722467] Call Trace:
[ 846.722814] process_one_work+0x1a7/0x3b0
[ 846.723157] worker_thread+0x30/0x390
[ 846.723501] ? create_worker+0x1a0/0x1a0
[ 846.723844] kthread+0x112/0x130
[ 846.724184] ? kthread_flush_work_fn+0x10/0x10
[ 846.724535] ret_from_fork+0x35/0x40
Now, check whether that ca is NULL in LINE#1655 to fix the issue.
The Linux kernel CVE team has assigned CVE-2025-38263 to this issue.
Affected and fixed versions
===========================
Fixed in 6.1.143 with commit c4f5e7e417034b05f5d2f5fa9a872db897da69bd
Fixed in 6.6.96 with commit 553f560e0a74a7008ad9dba05c3fd05da296befb
Fixed in 6.12.36 with commit 667c3f52373ff5354cb3543e27237eb7df7b2333
Fixed in 6.15.5 with commit 3f9e128186c99a117e304f1dce6d0b9e50c63cd8
Fixed in 6.16-rc1 with commit 1e46ed947ec658f89f1a910d880cd05e42d3763e
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-2025-38263
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:
drivers/md/bcache/super.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/c4f5e7e417034b05f5d2f5fa9a872db897da69bd
https://git.kernel.org/stable/c/553f560e0a74a7008ad9dba05c3fd05da296befb
https://git.kernel.org/stable/c/667c3f52373ff5354cb3543e27237eb7df7b2333
https://git.kernel.org/stable/c/3f9e128186c99a117e304f1dce6d0b9e50c63cd8
https://git.kernel.org/stable/c/1e46ed947ec658f89f1a910d880cd05e42d3763e
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