linux-cve-announce - CVE-2026-23214: btrfs: reject new transactions if the fs is fully read-only

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Message-ID: <2026021800-CVE-2026-23214-c822@gregkh>
Date: Wed, 18 Feb 2026 15:22:05 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23214: btrfs: reject new transactions if the fs is fully read-only

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

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

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

btrfs: reject new transactions if the fs is fully read-only

[BUG]
There is a bug report where a heavily fuzzed fs is mounted with all
rescue mount options, which leads to the following warnings during
unmount:

  BTRFS: Transaction aborted (error -22)
  Modules linked in:
  CPU: 0 UID: 0 PID: 9758 Comm: repro.out Not tainted
  6.19.0-rc5-00002-gb71e635feefc #7 PREEMPT(full)
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
  RIP: 0010:find_free_extent_update_loop fs/btrfs/extent-tree.c:4208 [inline]
  RIP: 0010:find_free_extent+0x52f0/0x5d20 fs/btrfs/extent-tree.c:4611
  Call Trace:
   <TASK>
   btrfs_reserve_extent+0x2cd/0x790 fs/btrfs/extent-tree.c:4705
   btrfs_alloc_tree_block+0x1e1/0x10e0 fs/btrfs/extent-tree.c:5157
   btrfs_force_cow_block+0x578/0x2410 fs/btrfs/ctree.c:517
   btrfs_cow_block+0x3c4/0xa80 fs/btrfs/ctree.c:708
   btrfs_search_slot+0xcad/0x2b50 fs/btrfs/ctree.c:2130
   btrfs_truncate_inode_items+0x45d/0x2350 fs/btrfs/inode-item.c:499
   btrfs_evict_inode+0x923/0xe70 fs/btrfs/inode.c:5628
   evict+0x5f4/0xae0 fs/inode.c:837
   __dentry_kill+0x209/0x660 fs/dcache.c:670
   finish_dput+0xc9/0x480 fs/dcache.c:879
   shrink_dcache_for_umount+0xa0/0x170 fs/dcache.c:1661
   generic_shutdown_super+0x67/0x2c0 fs/super.c:621
   kill_anon_super+0x3b/0x70 fs/super.c:1289
   btrfs_kill_super+0x41/0x50 fs/btrfs/super.c:2127
   deactivate_locked_super+0xbc/0x130 fs/super.c:474
   cleanup_mnt+0x425/0x4c0 fs/namespace.c:1318
   task_work_run+0x1d4/0x260 kernel/task_work.c:233
   exit_task_work include/linux/task_work.h:40 [inline]
   do_exit+0x694/0x22f0 kernel/exit.c:971
   do_group_exit+0x21c/0x2d0 kernel/exit.c:1112
   __do_sys_exit_group kernel/exit.c:1123 [inline]
   __se_sys_exit_group kernel/exit.c:1121 [inline]
   __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1121
   x64_sys_call+0x2210/0x2210 arch/x86/include/generated/asm/syscalls_64.h:232
   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
   do_syscall_64+0xe8/0xf80 arch/x86/entry/syscall_64.c:94
   entry_SYSCALL_64_after_hwframe+0x77/0x7f
  RIP: 0033:0x44f639
  Code: Unable to access opcode bytes at 0x44f60f.
  RSP: 002b:00007ffc15c4e088 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
  RAX: ffffffffffffffda RBX: 00000000004c32f0 RCX: 000000000044f639
  RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000001
  RBP: 0000000000000001 R08: ffffffffffffffc0 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004c32f0
  R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
   </TASK>

Since rescue mount options will mark the full fs read-only, there should
be no new transaction triggered.

But during unmount we will evict all inodes, which can trigger a new
transaction, and triggers warnings on a heavily corrupted fs.

[CAUSE]
Btrfs allows new transaction even on a read-only fs, this is to allow
log replay happen even on read-only mounts, just like what ext4/xfs do.

However with rescue mount options, the fs is fully read-only and cannot
be remounted read-write, thus in that case we should also reject any new
transactions.

[FIX]
If we find the fs has rescue mount options, we should treat the fs as
error, so that no new transaction can be started.

The Linux kernel CVE team has assigned CVE-2026-23214 to this issue.


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

	Fixed in 6.12.70 with commit a928eecf030a9a5dc5f5ca98332699f379b91963
	Fixed in 6.18.10 with commit 3228b2eceb6c3d7e237f8a5330113dbd164fb90d
	Fixed in 6.19 with commit 1972f44c189c8aacde308fa9284e474c1a5cbd9f

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-2026-23214
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/disk-io.c
	fs/btrfs/fs.h


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/a928eecf030a9a5dc5f5ca98332699f379b91963
	https://git.kernel.org/stable/c/3228b2eceb6c3d7e237f8a5330113dbd164fb90d
	https://git.kernel.org/stable/c/1972f44c189c8aacde308fa9284e474c1a5cbd9f