CVE-2026-90265

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

btrfs: defrag: fix deadlock between defrag and delalloc space reservation

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---