CVE-2026-45955 (GCVE-0-2026-45955)

Vulnerability from cvelistv5 – Published: 2026-05-27 12:18 – Updated: 2026-08-05 12:28
VLAI
Title
md/md-llbitmap: fix percpu_ref not resurrected on suspend timeout
Summary
In the Linux kernel, the following vulnerability has been resolved: md/md-llbitmap: fix percpu_ref not resurrected on suspend timeout When llbitmap_suspend_timeout() times out waiting for percpu_ref to become zero, it returns -ETIMEDOUT without resurrecting the percpu_ref. The caller (md_llbitmap_daemon_fn) then continues to the next page without calling llbitmap_resume(), leaving the percpu_ref in a killed state permanently. Fix this by resurrecting the percpu_ref before returning the error, ensuring the page control structure remains usable for subsequent operations.
Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 5ab829f1971dc99f2aac10846c378e67fc875abc , < 095417d6b669c2dec39a5842ccb94df915f97f54 (git)
Affected: 5ab829f1971dc99f2aac10846c378e67fc875abc , < 2446d099350185caeed19ab2c0270451a97296fb (git)
Affected: 5ab829f1971dc99f2aac10846c378e67fc875abc , < d119bd2e1643cc023210ff3c6f0657e4f914e71d (git)
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Linux Linux Affected: 6.18
Unaffected: 0 , < 6.18 (semver)
Unaffected: 6.18.14 , ≤ 6.18.* (semver)
Unaffected: 6.19.4 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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              "value": "AV:L - The flaw is in the MD lockless bitmap (`md-llbitmap`), reached only from the block/MD write path (`md_bitmap_start` \u2192 `llbitmap_start_write`), not from a network protocol handler. Any remote party must already cause writes through local VFS/block access (e.g., a file on an md-backed volume).\nAC:L - On a system with llbitmap enabled, an attacker can reliably force the timeout by racing the periodic daemon against many concurrent writes to the same bitmap page that hold `percpu_ref` until `daemon_sleep` expires; both sides of the race are attacker-driven I/O patterns.\nPR:L - Exploitation does not require real root in the init namespace: any principal that can issue writes to storage backed by an affected md array (typical unprivileged user on a multi-tenant NAS, or a member of the `disk` group with raw `/dev/md*` access) reaches the vulnerable code.\nUI:N - Triggering the race requires only sustained automated write I/O; no victim click, mount dialog, or other interactive action is needed beyond normal storage use.\nS:U - Impact stays within kernel/MD RAID scope (hang and bitmap inconsistency on the host); it does not cross a VM, container, or IOMMU security boundary.\nC:N - This is a refcount lifecycle logic bug, not memory corruption; there is no out-of-bounds access, UAF, or other primitive that discloses kernel memory.\nI:H - After the bug, `llbitmap_raise_barrier()` can block new writes before `llbitmap_state_machine()` runs, so dirty regions may not be recorded; combined with uncleared dirty bits on other paths, RAID resync decisions can be wrong after crash\u2014high integrity risk for redundant storage.\nA:H - A permanently killed `percpu_ref` leaves writers stuck in uninterruptible `wait_event` in `llbitmap_raise_barrier()`, causing indefinite write hangs (effective DoS) for affected bitmap pages on production NAS/RAID systems."
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      "title": "kernel: md/md-llbitmap: fix percpu_ref not resurrected on suspend timeout",
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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