---
id: CVE-2026-80808
title: 'ext4: stop retrying saturated xattr cache entries'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ext4: stop retrying saturated xattr cache entries

  ext4_xattr_block_set() retries when a cache entry selected for reuse
  has a saturated reference count after taking the…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1a56cd972ce121b6cf2517a47a578782bbd2ec95 <
    119a2f053242ed75bdd2ebc95baf3ae7db6ccacf
  - >-
    Linux >= 1be97463696c7291a3e1547614e96432b0bd3add <
    61631352a5b405c89be579de00903b72e6888aa4
  - >-
    Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b <
    8865cd664484517703df5c18a965dc3227572b87
  - >-
    Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b <
    a40c45268f4358207aa9c53764fed2e05f62986a
  - >-
    Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b <
    889ec86464d261f026f6c334040cfc6c58c99d58
  - >-
    Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b <
    4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9
  - >-
    Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b <
    55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5
  - >-
    Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b <
    dbd4aea175ad3c46436acb251e817b4374628072
  - >-
    Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b <
    54b6bd40898de7906acb2bccc9a96d1b8e6b4323
  - Linux 98953044b3cdb2cb7d82e7365b659e2ed4f4ca4d
  - Linux af8ecc8d20e72130771cc076bce7fcf17ccda6c4
  - Linux c6fac5cf5a5098732623bcd00a8a3eb9f5465144
  - Linux 96fa141fa295ae9428da73c56c9852053b575c04
  - Linux >= 5.10.163 < 5.10.267
  - Linux >= 5.15.61 < 5.15.218
  - Linux >= 4.19.270 < 4.20
  - Linux >= 5.4.229 < 5.5
  - Linux >= 5.18.18 < 5.19
  - Linux >= 5.19.2 < 5.20
  - Linux 6.0
published: '2026-09-04'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:44:01.677Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80808'
references:
  - url: 'https://git.kernel.org/stable/c/119a2f053242ed75bdd2ebc95baf3ae7db6ccacf'
  - url: 'https://git.kernel.org/stable/c/61631352a5b405c89be579de00903b72e6888aa4'
  - url: 'https://git.kernel.org/stable/c/8865cd664484517703df5c18a965dc3227572b87'
  - url: 'https://git.kernel.org/stable/c/a40c45268f4358207aa9c53764fed2e05f62986a'
  - url: 'https://git.kernel.org/stable/c/889ec86464d261f026f6c334040cfc6c58c99d58'
  - url: 'https://git.kernel.org/stable/c/4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9'
  - url: 'https://git.kernel.org/stable/c/55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5'
  - url: 'https://git.kernel.org/stable/c/dbd4aea175ad3c46436acb251e817b4374628072'
  - url: 'https://git.kernel.org/stable/c/54b6bd40898de7906acb2bccc9a96d1b8e6b4323'
tags:
  - cve.org
epss: 0.00195
epssPercentile: 0.08588
ingestedAt: '2026-10-19T09:16:01.524Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

ext4: stop retrying saturated xattr cache entries

ext4_xattr_block_set() retries when a cache entry selected for reuse
has a saturated reference count after taking the buffer lock. The retry
returns to the mbcache lookup without making that entry ineligible, so
it can select the same unusable entry indefinitely. A task spinning
there can hold the parent directory's i_rwsem and leave concurrent
rmdir callers blocked.

Normally a reusable entry has a reference count below
EXT4_XATTR_REFCOUNT_MAX because the count and MBE_REUSABLE_B are
updated under the same buffer lock. A corrupted filesystem can violate
that invariant. The syzbot reproducer reports allocator and xattr
corruption before triggering this retry loop.

Check the untrusted on-disk count before incrementing it, avoiding
overflow, and clear MBE_REUSABLE_B when it is already saturated. The
next lookup then skips the entry that was just proven unusable. This
mirrors the normal transition at EXT4_XATTR_REFCOUNT_MAX; the release
path marks the entry reusable again on the exact 1024-to-1023
transition.

Using the same QEMU harness and guest parameters, current unpatched
Linux hung in 6 of 8 420-second trials with the do_rmdir signature;
representative NMI backtraces caught the owner spinning in
ext4_xattr_block_set(). The patched kernel completed 28 of 28 trials
without a hung-task report; the final twelve trials exercised the
reviewed overflow-safe form of the change. syzbot's patch testing also
completed without reproducing the hang.

## Affected

- `Linux >= 1a56cd972ce121b6cf2517a47a578782bbd2ec95 < 119a2f053242ed75bdd2ebc95baf3ae7db6ccacf`
- `Linux >= 1be97463696c7291a3e1547614e96432b0bd3add < 61631352a5b405c89be579de00903b72e6888aa4`
- `Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b < 8865cd664484517703df5c18a965dc3227572b87`
- `Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b < a40c45268f4358207aa9c53764fed2e05f62986a`
- `Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b < 889ec86464d261f026f6c334040cfc6c58c99d58`
- `Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b < 4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9`
- `Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b < 55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5`
- `Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b < dbd4aea175ad3c46436acb251e817b4374628072`
- `Linux >= 65f8b80053a1b2fd602daa6814e62d6fa90e5e9b < 54b6bd40898de7906acb2bccc9a96d1b8e6b4323`
- `Linux 98953044b3cdb2cb7d82e7365b659e2ed4f4ca4d`
- `Linux af8ecc8d20e72130771cc076bce7fcf17ccda6c4`
- `Linux c6fac5cf5a5098732623bcd00a8a3eb9f5465144`
- `Linux 96fa141fa295ae9428da73c56c9852053b575c04`
- `Linux >= 5.10.163 < 5.10.267`
- `Linux >= 5.15.61 < 5.15.218`
- `Linux >= 4.19.270 < 4.20`
- `Linux >= 5.4.229 < 5.5`
- `Linux >= 5.18.18 < 5.19`
- `Linux >= 5.19.2 < 5.20`
- `Linux 6.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.