LiveActive security incident?Get immediate response
CVE Record

CVE-2022-48901: btrfs: do not start relocation until in progress drops are done

In the Linux kernel, the following vulnerability has been resolved: btrfs: do not start relocation until in progress drops are done We hit a bug with a recovering relocation on mount for one of our file systems in production. I reproduced this locally by injecting errors into snapshot delete with balance running at the same time. This presented as an error while looking up an extent item WARNING: CPU: 5 PID: 1501 at fs/btrfs/extent-tree.c:866 lookup_inline_extent_backref+0x647/0x680 CPU: 5 PID: 1501 Comm: btrfs-balance Not tainted 5.16.0-rc8+ #8 RIP: 0010:lookup_inline_extent_backref+0x647/0x680 RSP: 0018:ffffae0a023ab960 EFLAGS: 00010202 RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 000000000000000c RDI: 0000000000000000 RBP: ffff943fd2a39b60 R08: 0000000000000000 R09: 0000000000000001 R10: 0001434088152de0 R11: 0000000000000000 R12: 0000000001d05000 R13: ffff943fd2a39b60 R14: ffff943fdb96f2a0 R15: ffff9442fc923000 FS: 0000000000000000(0000) GS:ffff944e9eb40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f1157b1fca8 CR3: 000000010f092000 CR4: 0000000000350ee0 Call Trace: <TASK> insert_inline_extent_backref+0x46/0xd0 __btrfs_inc_extent_ref.isra.0+0x5f/0x200 ? btrfs_merge_delayed_refs+0x164/0x190 __btrfs_run_delayed_refs+0x561/0xfa0 ? btrfs_search_slot+0x7b4/0xb30 ? btrfs_update_root+0x1a9/0x2c0 btrfs_run_delayed_refs+0x73/0x1f0 ? btrfs_update_root+0x1a9/0x2c0 btrfs_commit_transaction+0x50/0xa50 ? btrfs_update_reloc_root+0x122/0x220 prepare_to_merge+0x29f/0x320 relocate_block_group+0x2b8/0x550 btrfs_relocate_block_group+0x1a6/0x350 btrfs_relocate_chunk+0x27/0xe0 btrfs_balance+0x777/0xe60 balance_kthread+0x35/0x50 ? btrfs_balance+0xe60/0xe60 kthread+0x16b/0x190 ? set_kthread_struct+0x40/0x40 ret_from_fork+0x22/0x30 </TASK> Normally snapshot deletion and relocation are excluded from running at the same time by the fs_info->cleaner_mutex. However if we had a pending balance waiting to get the ->cleaner_mutex, and a snapshot deletion was running, and then the box crashed, we would come up in a state where we have a half deleted snapshot. Again, in the normal case the snapshot deletion needs to complete before relocation can start, but in this case relocation could very well start before the snapshot deletion completes, as we simply add the root to the dead roots list and wait for the next time the cleaner runs to clean up the snapshot. Fix this by setting a bit on the fs_info if we have any DEAD_ROOT's that had a pending drop_progress key. If they do then we know we were in the middle of the drop operation and set a flag on the fs_info. Then balance can wait until this flag is cleared to start up again. If there are DEAD_ROOT's that don't have a drop_progress set then we're safe to start balance right away as we'll be properly protected by the cleaner_mutex.

UnknownCVSS not scoredNot KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2022-48901 is a Linux kernel Btrfs filesystem bug. After a crash during snapshot deletion, a later Btrfs balance operation could start too early and hit filesystem metadata errors. The issue is operationally important for systems relying on Btrfs snapshots and balance, but public sources do not show active exploitation.

Executive priority

Treat as a targeted reliability risk for Linux Btrfs environments, not a broadly exploitable emergency based on current sources. Prioritize patch validation where Btrfs snapshots support production, backup, or container workflows.

Technical view

The flaw is a race/order issue in Btrfs relocation recovery. Snapshot deletion and relocation are normally serialized by cleaner_mutex. After a crash with a half-deleted snapshot, relocation could begin before drop cleanup completed. The fix makes balance wait when dead roots have pending drop_progress.

Likely exposure

Exposure is most likely on Linux systems using Btrfs with snapshot deletion and balance operations. The source lists Linux kernel versions including 3.10, 5.15.27, 5.16.13, and 5.17 as affected, but version-range details are incomplete.

Exploitation context

The described trigger requires Btrfs operational conditions: snapshot deletion, balance/relocation, and a crash leaving pending drop work. KEV is false, and the provided sources do not report active exploitation or a remote attack path.

Researcher notes

Sources provide the kernel commit rationale but no CVSS, CWE, exploit report, or complete affected range semantics. Analysis should focus on Btrfs dead roots with pending drop_progress and balance start ordering after crash recovery.

Mitigation direction

  • Check your Linux vendor advisory for CVE-2022-48901 coverage.
  • Update to a kernel containing the referenced Btrfs stable fixes.
  • Prioritize hosts using Btrfs snapshots and scheduled balance operations.
  • Avoid unnecessary Btrfs balance during incident recovery until patched or vendor guidance is reviewed.

Validation and detection

  • Inventory systems using Btrfs filesystems.
  • Identify kernels in the affected version set or lacking the referenced commits.
  • Review logs for Btrfs balance, relocation, snapshot deletion, or extent warnings.
  • Confirm patched kernels include the upstream stable commits listed in sources.
Prepared
Confidence
medium
Sources
5

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

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2022-48901 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
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

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
1ADP providers
4Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux9d1a2a3ad59f7ae810bf04a5a05995bf2d79300c, 9d1a2a3ad59f7ae810bf04a5a05995bf2d79300c, 9d1a2a3ad59f7ae810bf04a5a05995bf2d79300cunaffected
LinuxLinux3.10, 0, 5.15.27, 5.16.13, 5.17affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.