FKIE_CVE-2026-80808

Vulnerability from fkie_nvd - Published: 2026-09-04 16:18 - Updated: 2026-10-19 09:17
Severity
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 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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/119a2f053242ed75bdd2ebc95baf3ae7db6ccacf
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/54b6bd40898de7906acb2bccc9a96d1b8e6b4323
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/61631352a5b405c89be579de00903b72e6888aa4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8865cd664484517703df5c18a965dc3227572b87
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/889ec86464d261f026f6c334040cfc6c58c99d58
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a40c45268f4358207aa9c53764fed2e05f62986a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/dbd4aea175ad3c46436acb251e817b4374628072
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ext4/xattr.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "119a2f053242ed75bdd2ebc95baf3ae7db6ccacf",
              "status": "affected",
              "version": "1a56cd972ce121b6cf2517a47a578782bbd2ec95",
              "versionType": "git"
            },
            {
              "lessThan": "61631352a5b405c89be579de00903b72e6888aa4",
              "status": "affected",
              "version": "1be97463696c7291a3e1547614e96432b0bd3add",
              "versionType": "git"
            },
            {
              "lessThan": "8865cd664484517703df5c18a965dc3227572b87",
              "status": "affected",
              "version": "65f8b80053a1b2fd602daa6814e62d6fa90e5e9b",
              "versionType": "git"
            },
            {
              "lessThan": "a40c45268f4358207aa9c53764fed2e05f62986a",
              "status": "affected",
              "version": "65f8b80053a1b2fd602daa6814e62d6fa90e5e9b",
              "versionType": "git"
            },
            {
              "lessThan": "889ec86464d261f026f6c334040cfc6c58c99d58",
              "status": "affected",
              "version": "65f8b80053a1b2fd602daa6814e62d6fa90e5e9b",
              "versionType": "git"
            },
            {
              "lessThan": "4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9",
              "status": "affected",
              "version": "65f8b80053a1b2fd602daa6814e62d6fa90e5e9b",
              "versionType": "git"
            },
            {
              "lessThan": "55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5",
              "status": "affected",
              "version": "65f8b80053a1b2fd602daa6814e62d6fa90e5e9b",
              "versionType": "git"
            },
            {
              "lessThan": "dbd4aea175ad3c46436acb251e817b4374628072",
              "status": "affected",
              "version": "65f8b80053a1b2fd602daa6814e62d6fa90e5e9b",
              "versionType": "git"
            },
            {
              "lessThan": "54b6bd40898de7906acb2bccc9a96d1b8e6b4323",
              "status": "affected",
              "version": "65f8b80053a1b2fd602daa6814e62d6fa90e5e9b",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "98953044b3cdb2cb7d82e7365b659e2ed4f4ca4d",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "af8ecc8d20e72130771cc076bce7fcf17ccda6c4",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "c6fac5cf5a5098732623bcd00a8a3eb9f5465144",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "96fa141fa295ae9428da73c56c9852053b575c04",
              "versionType": "git"
            },
            {
              "lessThan": "5.10.267",
              "status": "affected",
              "version": "5.10.163",
              "versionType": "semver"
            },
            {
              "lessThan": "5.15.218",
              "status": "affected",
              "version": "5.15.61",
              "versionType": "semver"
            },
            {
              "lessThan": "4.20",
              "status": "affected",
              "version": "4.19.270",
              "versionType": "semver"
            },
            {
              "lessThan": "5.5",
              "status": "affected",
              "version": "5.4.229",
              "versionType": "semver"
            },
            {
              "lessThan": "5.19",
              "status": "affected",
              "version": "5.18.18",
              "versionType": "semver"
            },
            {
              "lessThan": "5.20",
              "status": "affected",
              "version": "5.19.2",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/ext4/xattr.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.0"
            },
            {
              "lessThan": "6.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.267",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.218",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.185",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.154",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.106",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.47",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.1",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: stop retrying saturated xattr cache entries\n\next4_xattr_block_set() retries when a cache entry selected for reuse\nhas a saturated reference count after taking the buffer lock. The retry\nreturns to the mbcache lookup without making that entry ineligible, so\nit can select the same unusable entry indefinitely. A task spinning\nthere can hold the parent directory\u0027s i_rwsem and leave concurrent\nrmdir callers blocked.\n\nNormally a reusable entry has a reference count below\nEXT4_XATTR_REFCOUNT_MAX because the count and MBE_REUSABLE_B are\nupdated under the same buffer lock. A corrupted filesystem can violate\nthat invariant. The syzbot reproducer reports allocator and xattr\ncorruption before triggering this retry loop.\n\nCheck the untrusted on-disk count before incrementing it, avoiding\noverflow, and clear MBE_REUSABLE_B when it is already saturated. The\nnext lookup then skips the entry that was just proven unusable. This\nmirrors the normal transition at EXT4_XATTR_REFCOUNT_MAX; the release\npath marks the entry reusable again on the exact 1024-to-1023\ntransition.\n\nUsing the same QEMU harness and guest parameters, current unpatched\nLinux hung in 6 of 8 420-second trials with the do_rmdir signature;\nrepresentative NMI backtraces caught the owner spinning in\next4_xattr_block_set(). The patched kernel completed 28 of 28 trials\nwithout a hung-task report; the final twelve trials exercised the\nreviewed overflow-safe form of the change. syzbot\u0027s patch testing also\ncompleted without reproducing the hang."
    }
  ],
  "id": "CVE-2026-80808",
  "lastModified": "2026-10-19T09:17:15.520",
  "metrics": {},
  "published": "2026-09-04T16:18:07.993",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/119a2f053242ed75bdd2ebc95baf3ae7db6ccacf"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4902a5cba21aeaf91e6b29e20e0967a5f6abdcd9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/54b6bd40898de7906acb2bccc9a96d1b8e6b4323"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/55ee6533c1db7f7656fa8dd19637f3f8b8c08dc5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/61631352a5b405c89be579de00903b72e6888aa4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8865cd664484517703df5c18a965dc3227572b87"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/889ec86464d261f026f6c334040cfc6c58c99d58"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a40c45268f4358207aa9c53764fed2e05f62986a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/dbd4aea175ad3c46436acb251e817b4374628072"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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