CVE-2026-90265

What the bug is

While running fsstress with autodefrag and flushoncommit, hit a deadlock due to the fact that defrag reserves delalloc space while it's holding dirty and locked folios, besides the extent range lock. The stack traces are the following: [958.624] task:kworker/u50:3 state:D stack:0 pid:20365 tgid:20365 ppid:2 task_flags:0x4208060 flags:0x00080000 [958.626] Workqueue: events_unbound btrfs_async_reclaim_metadata_space [btrfs] [958.627] Call Trace: [958.628] <TASK> [958.628] __schedule+0x4be/0x10f0 [958.629] ? preempt_count_add+0x69/0xa0 [958.630] schedule+0x26/0xd0 [958.631] wait_current_trans+0x102/0x160 [btrfs] [958.632] ? __pfx_autoremove_wake_function+0x10/0x10 [958.633] start_transaction+0x374/0x900 [btrfs] [958.634] btrfs_commit_current_transaction+0x1d/0x70 [btrfs] [958.635] flush_space+0xca/0x5e0 [btrfs] [958.636] ? _raw_spin_unlock+0x15/0x30 [958.637] ? btrfs_reduce_alloc_profile+0x8c/0x190 [btrfs] [958.639] ? _raw_spin_unlock+0x15/0x30 [958.640] ? calc_available_free_space.isra.0+0x6f/0x110 [btrfs] [958.641] do_async_reclaim_metadata_space+0x84/0x190 [btrfs] [958.642] btrfs_async_reclaim_metadata_space+0x64/0x80 [btrfs] [958.644] process_one_work+0x19d/0x3a0 [958.644] worker_thread+0x1c4/0x330 [958.645] ? __pfx_worker_thread+0x10/0x10 [958.646] kthread+0xfc/0x130 [958.647] ? __pfx_kthread+0x10/0x10 [958.648] ret_from_fork+0x1f7/0x2c0 [958.648] ? __pfx_kthread+0x10/0x10 [958.649] ret_from_fork_asm+0x1a/0x30 [958.650] </TASK> [958.651] task:kworker/u49:7 state:D stack:0 pid:52990 tgid:52990 ppid:2 task_flags:0x4208060 flags:0x00080000 [958.653] Workqueue: writeback wb_workfn (flush-btrfs-334) [958.655] Call Trace: [958.655] <TASK> [958.656] __schedule+0x4be/0x10f0 [958.657] ? __blk_flush_plug+0xe9/0x140 [958.658] schedule+0x26/0xd0 [958.658] io_schedule+0x42/0x70 [958.659] folio_wait_bit_common+0x12b/0x330 [958.660] ? folio_wait_bit_common+0x100/0x330 [958.662] ? __pfx_wake_page_function+0x10/0x10 [958.663] extent_write_cache_pages+0x599/0x830 [btrfs] [958.664] ? acpi_fwnode_get_reference_args+0x1fa/0x270 [958.665] btrfs_writepages+0x77/0x130 [btrfs] [958.666] ? __pfx_end_bbio_data_write+0x10/0x10 [btrfs] [958.667] do_writepages+0xc6/0x160 [958.668] __writeback_single_inode+0x42/0x310 [958.669] writeback_sb_inodes+0x231/0x570 [958.670] wb_writeback+0x8a/0x340 [958.671] wb_workfn+0xbf/0x450 [958.672] ? finish_task_switch.isra.0+0xc1/0x350 [958.673] process_one_work+0x19d/0x3a0 [958.673] worker_thread+0x1c4/0x330 [958.674] ? __pfx_worker_thread+0x10/0x10 [958.675] kthread+0xfc/0x130 [958.676] ? __pfx_kthread+0x10/0x10 [958.676] ret_from_fork+0x1f7/0x2c0 [958.677] ? __pfx_kthread+0x10/0x10 [958.678] ret_from_fork_asm+0x1a/0x30 [958.679] </TASK> [958.679] task:btrfs-cleaner state:D stack:0 pid:296750 tgid:296750 ppid:2 task_flags:0x208040 flags:0x00080000 [958.681] Call Trace: [958.682] <TASK> [958.682] __schedule+0x4be/0x10f0 [958.683] schedule+0x26/0xd0 [958.684] handle_reserve_ticket+0x1b9/0x2c0 [btrfs] [958.685] ? __pfx_autoremove_wake_function+0x10/0x10 [958.686] reserve_bytes+0x283/0x4c0 [btrfs] [958.687] btrfs_reserve_metadata_bytes+0x18/0xb0 [btrfs] [958.688] btrfs_delalloc_reserve_metadata+0x121/0x320 [btrfs] [958.690] btrfs_delalloc_reserve_space+0x46/0xb0 [btrfs] [958.691] btrfs_defrag_file+0x903/0x1110 [btrfs] [958.692] btrfs_run_defrag_inodes+0x334/0x430 [btrfs] [958.694] cleaner_kthread+0x97/0x1c0 [btrfs] [958.694] ? __pfx_cleaner_kthread+0x10/0x10 [btrfs] [958.696] kthread+0xfc/0x130 [958.696] ? __pfx_kthread+0x10/0x10 [958.697] ret_ ---truncated---

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

fs/btrfs/defrag.c

What this is

BTRFS FILE SYSTEMMAINTAINERS section matched on fs/btrfs/ · linux-btrfs@vger.kernel.org · Maintained

Kernel module

btrfs

Check it on the machine

grep -w CONFIG_BTRFS_FS /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

lsmod | grep -w btrfs

Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.

Show whether Debian builds this, per release

Debian builds this as a loadable module. Every release with an answer below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded. The build rule could not be established for 1 release, so nothing is claimed about those.

• bookworm?
• trixie, forky, sidm

?

not established - no Makefile entry for the affected file

m

a loadable module on every flavour - check lsmod, can be blacklisted

Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.

Build switch

CONFIG_BTRFS_FS

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-09-17 (31 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.21%, higher than 10.0% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

fs/btrfs

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
5.16	6.18.52	a9701dd06e82
5.16	7.2.6	ac916391e1c7
5.16	7.3	ba02eab28041