* CVE-2026-46251: btrfs: fix block_group_tree dirty_list corruption
@ 2026-06-03 15:49 Greg Kroah-Hartman
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From: Greg Kroah-Hartman @ 2026-06-03 15:49 UTC (permalink / raw)
To: linux-cve-announce; +Cc: Greg Kroah-Hartman
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix block_group_tree dirty_list corruption
When the incompat flag EXTENT_TREE_V2 is set, we unconditionally add the
block group tree to the switch_commits list before calling
switch_commit_roots, as we do for the tree root and the chunk root.
However, the block group tree uses normal root dirty tracking and in any
transaction that does an allocation and dirties a block group, the block
group root will already be linked to a list by the dirty_list field and
this use of list_add_tail() is invalid and corrupts the prev/next
members of block_group_root->dirty_list.
This is apparent on a subsequent list_del on the prev if we enable
CONFIG_DEBUG_LIST:
[32.1571] ------------[ cut here ]------------
[32.1572] list_del corruption. next->prev should beffff958890202538, but was ffff9588992bd538. (next=ffff958890201538)
[32.1575] WARNING: lib/list_debug.c:65 at 0x0, CPU#3: sync/607
[32.1583] CPU: 3 UID: 0 PID: 607 Comm: sync Not tainted 6.18.0 #24PREEMPT(none)
[32.1585] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS1.17.0-4.fc41 04/01/2014
[32.1587] RIP: 0010:__list_del_entry_valid_or_report+0x108/0x120
[32.1593] RSP: 0018:ffffaa288287fdd0 EFLAGS: 00010202
[32.1594] RAX: 0000000000000001 RBX: ffff95889326e800 RCX:ffff958890201538
[32.1596] RDX: ffff9588992bd538 RSI: ffff958890202538 RDI:ffffffff82a41e00
[32.1597] RBP: ffff958890202538 R08: ffffffff828fc1e8 R09:00000000ffffefff
[32.1599] R10: ffffffff8288c200 R11: ffffffff828e4200 R12:ffff958890201538
[32.1601] R13: ffff95889326e958 R14: ffff958895c24000 R15:ffff958890202538
[32.1603] FS: 00007f0c28eb5740(0000) GS:ffff958af2bd2000(0000)knlGS:0000000000000000
[32.1605] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[32.1607] CR2: 00007f0c28e8a3cc CR3: 0000000109942005 CR4:0000000000370ef0
[32.1609] Call Trace:
[32.1610] <TASK>
[32.1611] switch_commit_roots+0x82/0x1d0 [btrfs]
[32.1615] btrfs_commit_transaction+0x968/0x1550 [btrfs]
[32.1618] ? btrfs_attach_transaction_barrier+0x23/0x60 [btrfs]
[32.1621] __iterate_supers+0xe8/0x190
[32.1622] ? __pfx_sync_fs_one_sb+0x10/0x10
[32.1623] ksys_sync+0x63/0xb0
[32.1624] __do_sys_sync+0xe/0x20
[32.1625] do_syscall_64+0x73/0x450
[32.1626] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[32.1627] RIP: 0033:0x7f0c28d05d2b
[32.1632] RSP: 002b:00007ffc9d988048 EFLAGS: 00000246 ORIG_RAX:00000000000000a2
[32.1634] RAX: ffffffffffffffda RBX: 00007ffc9d988228 RCX:00007f0c28d05d2b
[32.1636] RDX: 00007f0c28e02301 RSI: 00007ffc9d989b21 RDI:00007f0c28dba90d
[32.1637] RBP: 0000000000000001 R08: 0000000000000001 R09:0000000000000000
[32.1639] R10: 0000000000000000 R11: 0000000000000246 R12:000055b96572cb80
[32.1641] R13: 000055b96572b19f R14: 00007f0c28dfa434 R15:000055b96572b034
[32.1643] </TASK>
[32.1644] irq event stamp: 0
[32.1644] hardirqs last enabled at (0): [<0000000000000000>] 0x0
[32.1646] hardirqs last disabled at (0): [<ffffffff81298817>]copy_process+0xb37/0x2260
[32.1648] softirqs last enabled at (0): [<ffffffff81298817>]copy_process+0xb37/0x2260
[32.1650] softirqs last disabled at (0): [<0000000000000000>] 0x0
[32.1652] ---[ end trace 0000000000000000 ]---
Furthermore, this list corruption eventually (when we happen to add a
new block group) results in getting the switch_commits and
dirty_cowonly_roots lists mixed up and attempting to call update_root
on the tree root which can't be found in the tree root, resulting in a
transaction abort:
[87.8269] BTRFS critical (device nvme1n1): unable to find root key (1 0 0) in tree 1
[87.8272] ------------[ cut here ]------------
[87.8274] BTRFS: Transaction aborted (error -117)
[87.8275] WARNING: fs/btrfs/root-tree.c:153 at 0x0, CPU#4: sync/703
[87.8285] CPU: 4 UID: 0 PID: 703 Comm: sync Not tainted 6.18.0 #25 PREEMPT(none)
[87.8287] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-4.fc41 04/01/2014
[87.8289] RIP: 0010:btrfs_update_root+0x296/0x790 [btrfs]
[87.8295] RSP: 0018:ffffa58d035dfd60 EFLAGS: 00010282
[87.8297] RAX: ffff9a59126ddb68 RBX: ffff9a59126dc000 RCX: 0000000000000000
[87.8299] RDX: 0000000000000000 RSI: 00000000ffffff8b RDI: ffffffffc0b28270
[87.8301] RBP: ffff9a5904aec000 R08: 0000000000000000 R09: 00000000ffffefff
[87.8303] R10: ffffffff9ac8c200 R11: ffffffff9ace4200 R12: 0000000000000001
[87.8305] R13: ffff9a59041740e8 R14: ffff9a5904aec1f7 R15: ffff9a590fdefaf0
[87.8307] FS: 00007f54cde6b740(0000) GS:ffff9a5b5a81c000(0000) knlGS:0000000000000000
[87.8309] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[87.8310] CR2: 00007f54cde403cc CR3: 0000000112902004 CR4: 0000000000370ef0
[87.8312] Call Trace:
[87.8313] <TASK>
[87.8314] ? _raw_spin_unlock+0x23/0x40
[87.8315] commit_cowonly_roots+0x1ad/0x250 [btrfs]
[87.8317] ? btrfs_commit_transaction+0x79b/0x1560 [btrfs]
[87.8320] btrfs_commit_transaction+0x8aa/0x1560 [btrfs]
[87.8322] ? btrfs_attach_transaction_barrier+0x23/0x60 [btrfs]
[87.8325] __iterate_supers+0xf1/0x170
[87.8326] ? __pfx_sync_fs_one_sb+0x10/0x10
[87.8327] ksys_sync+0x63/0xb0
[87.8328] __do_sys_sync+0xe/0x20
[87.8329] do_syscall_64+0x73/0x450
[87.8330] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[87.8331] RIP: 0033:0x7f54cdd05d2b
[87.8336] RSP: 002b:00007fff1b58ff78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
[87.8338] RAX: ffffffffffffffda RBX: 00007fff1b590158 RCX: 00007f54cdd05d2b
[87.8340] RDX: 00007f54cde02301 RSI: 00007fff1b592b66 RDI: 00007f54cddba90d
[87.8342] RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
[87.8344] R10: 0000000000000000 R11: 0000000000000246 R12: 000055e07ca96b80
[87.8346] R13: 000055e07ca9519f R14: 00007f54cddfa434 R15: 000055e07ca95034
[87.8348] </TASK>
[87.8348] irq event stamp: 0
[87.8349] hardirqs last enabled at (0): [<0000000000000000>] 0x0
[87.8351] hardirqs last disabled at (0): [<ffffffff99698797>] copy_process+0xb37/0x21e0
[87.8353] softirqs last enabled at (0): [<ffffffff99698797>] copy_process+0xb37/0x21e0
[87.8355] softirqs last disabled at (0): [<0000000000000000>] 0x0
[87.8357] ---[ end trace 0000000000000000 ]---
[87.8358] BTRFS: error (device nvme1n1 state A) in btrfs_update_root:153: errno=-117 Filesystem corrupted
[87.8360] BTRFS info (device nvme1n1 state EA): forced readonly
[87.8362] BTRFS warning (device nvme1n1 state EA): Skipping commit of aborted transaction.
[87.8364] BTRFS: error (device nvme1n1 state EA) in cleanup_transaction:2037: errno=-117 Filesystem corrupted
Since the block group tree was pulled out of the extent tree and uses
normal root dirty tracking, remove the offending extra list_add. This
fixes the list corruption and the resulting fs corruption.
The Linux kernel CVE team has assigned CVE-2026-46251 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.1 with commit 14033b08a02916e85ffc5397e4ac15337359f3ae and fixed in 6.1.165 with commit 6e10283b5519d987d880d71bec90cdc7f2ec62b3
Issue introduced in 6.1 with commit 14033b08a02916e85ffc5397e4ac15337359f3ae and fixed in 6.6.128 with commit e3d1fd084319f8f0830b22f014c7af6a96b4497b
Issue introduced in 6.1 with commit 14033b08a02916e85ffc5397e4ac15337359f3ae and fixed in 6.12.75 with commit 4eb830847d84276f1c8ea46541cfeeedaba1fb63
Issue introduced in 6.1 with commit 14033b08a02916e85ffc5397e4ac15337359f3ae and fixed in 6.18.14 with commit 80e1fda9c084dcf54819a12bc7682ec0afd2d8f4
Issue introduced in 6.1 with commit 14033b08a02916e85ffc5397e4ac15337359f3ae and fixed in 6.19.4 with commit 201091da34c4f113af6b4a7407091c39bf29d4ca
Issue introduced in 6.1 with commit 14033b08a02916e85ffc5397e4ac15337359f3ae and fixed in 7.0 with commit 3a1f4264daed4b419c325a7fe35e756cada3cf82
Issue introduced in 6.0.19 with commit dabf41db56f378a360ff0219c467f8dfecda7dd6
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-2026-46251
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:
fs/btrfs/transaction.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/6e10283b5519d987d880d71bec90cdc7f2ec62b3
https://git.kernel.org/stable/c/e3d1fd084319f8f0830b22f014c7af6a96b4497b
https://git.kernel.org/stable/c/4eb830847d84276f1c8ea46541cfeeedaba1fb63
https://git.kernel.org/stable/c/80e1fda9c084dcf54819a12bc7682ec0afd2d8f4
https://git.kernel.org/stable/c/201091da34c4f113af6b4a7407091c39bf29d4ca
https://git.kernel.org/stable/c/3a1f4264daed4b419c325a7fe35e756cada3cf82
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