CVE-2022-49702 | btrfs: fix hang during unmount when block group reclaim task is running

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix hang during unmount when block group reclaim task is running When we start an unmount, at close_ctree(), if we have the reclaim task running and in the middle of a data block group relocation, we can trigger a deadlock when stopping an async reclaim task, producing a trace like the following: [629724.498185] task:kworker/u16:7 state:D stack: 0 pid:681170 ppid: 2 flags:0x00004000 [629724.499760] Workqueue: events_unbound btrfs_async_reclaim_metadata_space [btrfs] [629724.501267] Call Trace: [629724.501759] <TASK> [629724.502174] __schedule+0x3cb/0xed0 [629724.502842] schedule+0x4e/0xb0 [629724.503447] btrfs_wait_on_delayed_iputs+0x7c/0xc0 [btrfs] [629724.504534] ? prepare_to_wait_exclusive+0xc0/0xc0 [629724.505442] flush_space+0x423/0x630 [btrfs] [629724.506296] ? rcu_read_unlock_trace_special+0x20/0x50 [629724.507259] ? lock_release+0x220/0x4a0 [629724.507932] ? btrfs_get_alloc_profile+0xb3/0x290 [btrfs] [629724.508940] ? do_raw_spin_unlock+0x4b/0xa0 [629724.509688] btrfs_async_reclaim_metadata_space+0x139/0x320 [btrfs] [629724.510922] process_one_work+0x252/0x5a0 [629724.511694] ? process_one_work+0x5a0/0x5a0 [629724.512508] worker_thread+0x52/0x3b0 [629724.513220] ? process_one_work+0x5a0/0x5a0 [629724.514021] kthread+0xf2/0x120 [629724.514627] ? kthread_complete_and_exit+0x20/0x20 [629724.515526] ret_from_fork+0x22/0x30 [629724.516236] </TASK> [629724.516694] task:umount state:D stack: 0 pid:719055 ppid:695412 flags:0x00004000 [629724.518269] Call Trace: [629724.518746] <TASK> [629724.519160] __schedule+0x3cb/0xed0 [629724.519835] schedule+0x4e/0xb0 [629724.520467] schedule_timeout+0xed/0x130 [629724.521221] ? lock_release+0x220/0x4a0 [629724.521946] ? lock_acquired+0x19c/0x420 [629724.522662] ? trace_hardirqs_on+0x1b/0xe0 [629724.523411] __wait_for_common+0xaf/0x1f0 [629724.524189] ? usleep_range_state+0xb0/0xb0 [629724.524997] __flush_work+0x26d/0x530 [629724.525698] ? flush_workqueue_prep_pwqs+0x140/0x140 [629724.526580] ? lock_acquire+0x1a0/0x310 [629724.527324] __cancel_work_timer+0x137/0x1c0 [629724.528190] close_ctree+0xfd/0x531 [btrfs] [629724.529000] ? evict_inodes+0x166/0x1c0 [629724.529510] generic_shutdown_super+0x74/0x120 [629724.530103] kill_anon_super+0x14/0x30 [629724.530611] btrfs_kill_super+0x12/0x20 [btrfs] [629724.531246] deactivate_locked_super+0x31/0xa0 [629724.531817] cleanup_mnt+0x147/0x1c0 [629724.532319] task_work_run+0x5c/0xa0 [629724.532984] exit_to_user_mode_prepare+0x1a6/0x1b0 [629724.533598] syscall_exit_to_user_mode+0x16/0x40 [629724.534200] do_syscall_64+0x48/0x90 [629724.534667] entry_SYSCALL_64_after_hwframe+0x44/0xae [629724.535318] RIP: 0033:0x7fa2b90437a7 [629724.535804] RSP: 002b:00007ffe0b7e4458 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6 [629724.536912] RAX: 0000000000000000 RBX: 00007fa2b9182264 RCX: 00007fa2b90437a7 [629724.538156] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000555d6cf20dd0 [629724.539053] RBP: 0000555d6cf20ba0 R08: 0000000000000000 R09: 00007ffe0b7e3200 [629724.539956] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [629724.540883] R13: 0000555d6cf20dd0 R14: 0000555d6cf20cb0 R15: 0000000000000000 [629724.541796] </TASK> This happens because: 1) Before entering close_ctree() we have the async block group reclaim task running and relocating a data block group; 2) There's an async metadata (or data) space reclaim task running; 3) We enter close_ctree() and park the cleaner kthread; 4) The async space reclaim task is at flush_space() and runs all the existing delayed iputs; 5) Before the async space reclaim task calls btrfs_wait_on_delayed_iputs(), the block group reclaim task which is doing the data block group relocation, creates a delayed iput at replace_file_extents() (called when COWing leaves that have file extent items pointing to relocated data exten ---truncated---

Published: 2025-02-26 Last update: 2025-10-24 Assigner: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2022-49702 is rated Low Risk (25.4/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.19%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2022-49702

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.05% 0.19% +0.14%
2 2026-04-06 0.04% 0.05% +0.01%
3 2025-07-22 — 0.04% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2022-49702

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]

Weakness enumeration for CVE-2022-49702

OS Trackers for CVE-2022-49702

vendor priority summary link
debian unimportant CVE-2022-49702 unimportant priority: Debian including 1 source packages (linux), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2022-49702
redhat medium — https://access.redhat.com/security/cve/CVE-2022-49702
suse medium CVE-2022-49702 severity moderate: SUSE including 26 source package names (cluster-md-kmp-default, dlm-kmp-default, …), 198 product×package rows across 36 product lines (SLES-LTSS-TERADATA 15 SP2, SUSE Linux Enterprise High Availability Extension 12 SP5, … (36 product lines)): Known Not Affected 198. https://www.suse.com/security/cve/CVE-2022-49702/
ubuntu medium CVE-2022-49702 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1551 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 1145, ignored 146, not-affected 145, released 114, needs-triage 1. https://ubuntu.com/security/CVE-2022-49702

Affected software / configurations for CVE-2022-49702

Vendor Product Version Raw CPE
linux linux_kernel >= 5.13, < 5.15.51 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 5.16, < 5.18.8 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel 5.19 cpe:2.3:o:linux:linux_kernel:5.19:rc1:*:*:*:*:*:*
linux linux_kernel 5.19 cpe:2.3:o:linux:linux_kernel:5.19:rc2:*:*:*:*:*:*
linux linux_kernel 5.19 cpe:2.3:o:linux:linux_kernel:5.19:rc3:*:*:*:*:*:*

References for CVE-2022-49702

cvelogic Threat Intelligence