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CVE Record

CVE-2022-50089: btrfs: ensure pages are unlocked on cow_file_range() failure

In the Linux kernel, the following vulnerability has been resolved: btrfs: ensure pages are unlocked on cow_file_range() failure There is a hung_task report on zoned btrfs like below. https://github.com/naota/linux/issues/59 [726.328648] INFO: task rocksdb:high0:11085 blocked for more than 241 seconds. [726.329839] Not tainted 5.16.0-rc1+ #1 [726.330484] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [726.331603] task:rocksdb:high0 state:D stack: 0 pid:11085 ppid: 11082 flags:0x00000000 [726.331608] Call Trace: [726.331611] <TASK> [726.331614] __schedule+0x2e5/0x9d0 [726.331622] schedule+0x58/0xd0 [726.331626] io_schedule+0x3f/0x70 [726.331629] __folio_lock+0x125/0x200 [726.331634] ? find_get_entries+0x1bc/0x240 [726.331638] ? filemap_invalidate_unlock_two+0x40/0x40 [726.331642] truncate_inode_pages_range+0x5b2/0x770 [726.331649] truncate_inode_pages_final+0x44/0x50 [726.331653] btrfs_evict_inode+0x67/0x480 [726.331658] evict+0xd0/0x180 [726.331661] iput+0x13f/0x200 [726.331664] do_unlinkat+0x1c0/0x2b0 [726.331668] __x64_sys_unlink+0x23/0x30 [726.331670] do_syscall_64+0x3b/0xc0 [726.331674] entry_SYSCALL_64_after_hwframe+0x44/0xae [726.331677] RIP: 0033:0x7fb9490a171b [726.331681] RSP: 002b:00007fb943ffac68 EFLAGS: 00000246 ORIG_RAX: 0000000000000057 [726.331684] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb9490a171b [726.331686] RDX: 00007fb943ffb040 RSI: 000055a6bbe6ec20 RDI: 00007fb94400d300 [726.331687] RBP: 00007fb943ffad00 R08: 0000000000000000 R09: 0000000000000000 [726.331688] R10: 0000000000000031 R11: 0000000000000246 R12: 00007fb943ffb000 [726.331690] R13: 00007fb943ffb040 R14: 0000000000000000 R15: 00007fb943ffd260 [726.331693] </TASK> While we debug the issue, we found running fstests generic/551 on 5GB non-zoned null_blk device in the emulated zoned mode also had a similar hung issue. Also, we can reproduce the same symptom with an error injected cow_file_range() setup. The hang occurs when cow_file_range() fails in the middle of allocation. cow_file_range() called from do_allocation_zoned() can split the give region ([start, end]) for allocation depending on current block group usages. When btrfs can allocate bytes for one part of the split regions but fails for the other region (e.g. because of -ENOSPC), we return the error leaving the pages in the succeeded regions locked. Technically, this occurs only when @unlock == 0. Otherwise, we unlock the pages in an allocated region after creating an ordered extent. Considering the callers of cow_file_range(unlock=0) won't write out the pages, we can unlock the pages on error exit from cow_file_range(). So, we can ensure all the pages except @locked_page are unlocked on error case. In summary, cow_file_range now behaves like this: - page_started == 1 (return value) - All the pages are unlocked. IO is started. - unlock == 1 - All the pages except @locked_page are unlocked in any case - unlock == 0 - On success, all the pages are locked for writing out them - On failure, all the pages except @locked_page are unlocked

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel btrfs flaw can leave filesystem pages locked after a failed copy-on-write allocation, causing tasks to hang. The clearest business impact is availability: affected systems using btrfs, especially zoned or emulated zoned storage, may experience stuck workloads during allocation failure conditions such as low space.

Executive priority

Treat this as an availability maintenance issue, not an emergency based on current evidence. Patch during normal kernel update cycles, with higher priority for storage-heavy btrfs deployments where hangs could affect production workloads.

Technical view

The issue is in btrfs cow_file_range() error handling. When called with unlock=0 from zoned allocation paths, a partial allocation failure could return without unlocking pages from successful split regions. The fix changes failure handling so pages except locked_page are unlocked on error.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions with btrfs, especially zoned btrfs or emulated zoned devices. Systems not using btrfs are not directly exposed by the described bug.

Exploitation context

The source describes reproducible hangs using fstests and error injection, not public exploitation. The CVE is not marked KEV, and the supplied sources do not claim active exploitation or a weaponized attack path.

Researcher notes

Evidence centers on a kernel logic bug in btrfs page unlock behavior after partial cow_file_range() failure. The supplied record lacks CVSS, CWE, exploitability details, and distribution-specific affected ranges, so validation should rely on kernel and vendor backport status.

Mitigation direction

  • Prioritize kernel updates containing the referenced stable btrfs fixes.
  • Identify systems using btrfs, especially zoned or emulated zoned configurations.
  • Check vendor kernel advisories for backported fixes in distribution kernels.
  • Monitor affected hosts for hung_task reports and blocked filesystem workloads.

Validation and detection

  • Confirm running kernel versions against vendor advisories and stable fix commits.
  • Inventory mounted filesystems and identify btrfs usage.
  • Review logs for hung_task reports involving btrfs, unlink, truncate, or eviction paths.
  • Verify patched kernels no longer reproduce the documented failure in safe test environments.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

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0CVSS vectors
3Timeline events
0ADP providers
5Source links

Vulnerability timeline

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  1. CVE reservedCVE Program

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  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux42c011000963442ce533d92a492c4a057b2f5a46, 42c011000963442ce533d92a492c4a057b2f5a46, 42c011000963442ce533d92a492c4a057b2f5a46, 42c011000963442ce533d92a492c4a057b2f5a46unaffected
LinuxLinux5.12, 0, 5.15.61, 5.18.18, 5.19.2, 6.0affected
Weakness

CWE details

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