CVE-2022-50571 btrfs: call __btrfs_remove_free_space_cache_locked on cache load failure
A flaw in the Linux kernel's Btrfs filesystem can cause a kernel warning and potential denial of service when free space cache loading fails.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2022-50571?
CVE-2022-50571 is a denial of service vulnerability in Linux, published on 22 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
btrfs: call __btrfs_remove_free_space_cache_locked on cache load failure
Now that lockdep is staying enabled through our entire CI runs I started seeing the following stack in generic/475
------------[ cut here ]------------ WARNING: CPU: 1 PID: 2171864 at fs/btrfs/discard.c:604 btrfs_discard_update_discardable+0x98/0xb0 CPU: 1 PID: 2171864 Comm: kworker/u4:0 Not tainted 5.19.0-rc8+ #789 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 Workqueue: btrfs-cache btrfs_work_helper RIP: 0010:btrfs_discard_update_discardable+0x98/0xb0 RSP: 0018:ffffb857c2f7bad0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff8c85c605c200 RCX: 0000000000000001 RDX: 0000000000000000 RSI: ffffffff86807c5b RDI: ffffffff868a831e RBP: ffff8c85c4c54000 R08: 0000000000000000 R09: 0000000000000000 R10: ffff8c85c66932f0 R11: 0000000000000001 R12: ffff8c85c3899010 R13: ffff8c85d5be4f40 R14: ffff8c85c4c54000 R15: ffff8c86114bfa80 FS: 0000000000000000(0000) GS:ffff8c863bd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2e7f168160 CR3: 000000010289a004 CR4: 0000000000370ee0 Call Trace:
__btrfs_remove_free_space_cache+0x27/0x30 load_free_space_cache+0xad2/0xaf0 caching_thread+0x40b/0x650 ? lock_release+0x137/0x2d0 btrfs_work_helper+0xf2/0x3e0 ? lock_is_held_type+0xe2/0x140 process_one_work+0x271/0x590 ? process_one_work+0x590/0x590 worker_thread+0x52/0x3b0 ? process_one_work+0x590/0x590 kthread+0xf0/0x120 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x1f/0x30
This is the code
ctl = block_group->free_space_ctl; discard_ctl = &block_group->fs_info->discard_ctl;
lockdep_assert_held(&ctl->tree_lock);
We have a temporary free space ctl for loading the free space cache in order to avoid having allocations happening while we're loading the cache. When we hit an error we free it all up, however this also calls btrfs_discard_update_discardable, which requires block_group->free_space_ctl->tree_lock to be held. However this is our temporary ctl so this lock isn't held. Fix this by calling __btrfs_remove_free_space_cache_locked instead so that we only clean up the entries and do not mess with the discardable stats.
Which versions are affected by CVE-2022-50571?
How do I fix CVE-2022-50571?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2022-50571 being exploited?
There is no known exploitation of CVE-2022-50571 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2022-50571, GHSA-3w5q-vc28-c92f, ROOT-OS-UBUNTU-2204-CVE-2022-50571, UBUNTU-CVE-2022-50571.