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CVE-2022-50668 (GCVE-0-2022-50668)

Vulnerability from cvelistv5 – Published: 2025-12-09 01:29 – Updated: 2026-08-05 08:59
VLAI
Title
ext4: fix deadlock due to mbcache entry corruption
Summary
In the Linux kernel, the following vulnerability has been resolved: ext4: fix deadlock due to mbcache entry corruption When manipulating xattr blocks, we can deadlock infinitely looping inside ext4_xattr_block_set() where we constantly keep finding xattr block for reuse in mbcache but we are unable to reuse it because its reference count is too big. This happens because cache entry for the xattr block is marked as reusable (e_reusable set) although its reference count is too big. When this inconsistency happens, this inconsistent state is kept indefinitely and so ext4_xattr_block_set() keeps retrying indefinitely. The inconsistent state is caused by non-atomic update of e_reusable bit. e_reusable is part of a bitfield and e_reusable update can race with update of e_referenced bit in the same bitfield resulting in loss of one of the updates. Fix the problem by using atomic bitops instead. This bug has been around for many years, but it became *much* easier to hit after commit 65f8b80053a1 ("ext4: fix race when reusing xattr blocks").
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 6048c64b26097a0ffbd966866b599f990e674e9b , < efaa0ca678f56d47316a08030b2515678cebbc50 (git)
Affected: 6048c64b26097a0ffbd966866b599f990e674e9b , < af53065276376750dfac35a7248af18806404c5d (git)
Affected: 6048c64b26097a0ffbd966866b599f990e674e9b , < 1be16a0c2f10186df505e28b0cc92d7f3366e2a8 (git)
Affected: 6048c64b26097a0ffbd966866b599f990e674e9b , < 5bc0b2fda4b47c86278f7c6d30c211f425bf51cf (git)
Affected: 6048c64b26097a0ffbd966866b599f990e674e9b , < 127b80cefb941a81255c72f11081123f3a705369 (git)
Affected: 6048c64b26097a0ffbd966866b599f990e674e9b , < cc1538c693d25e282bed8c54b65c914a04023a78 (git)
Affected: 6048c64b26097a0ffbd966866b599f990e674e9b , < a44e84a9b7764c72896f7241a0ec9ac7e7ef38dd (git)
guessed Create a notification for this product.
Linux Linux Affected: 4.6
Unaffected: 0 , < 4.6 (semver)
Unaffected: 4.19.270 , ≤ 4.19.* (semver)
Unaffected: 5.4.229 , ≤ 5.4.* (semver)
Unaffected: 5.10.163 , ≤ 5.10.* (semver)
Unaffected: 5.15.87 , ≤ 5.15.* (semver)
Unaffected: 6.0.18 , ≤ 6.0.* (semver)
Unaffected: 6.1.4 , ≤ 6.1.* (semver)
Unaffected: 6.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ext4/xattr.c",
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix deadlock due to mbcache entry corruption\n\nWhen manipulating xattr blocks, we can deadlock infinitely looping\ninside ext4_xattr_block_set() where we constantly keep finding xattr\nblock for reuse in mbcache but we are unable to reuse it because its\nreference count is too big. This happens because cache entry for the\nxattr block is marked as reusable (e_reusable set) although its\nreference count is too big. When this inconsistency happens, this\ninconsistent state is kept indefinitely and so ext4_xattr_block_set()\nkeeps retrying indefinitely.\n\nThe inconsistent state is caused by non-atomic update of e_reusable bit.\ne_reusable is part of a bitfield and e_reusable update can race with\nupdate of e_referenced bit in the same bitfield resulting in loss of one\nof the updates. Fix the problem by using atomic bitops instead.\n\nThis bug has been around for many years, but it became *much* easier\nto hit after commit 65f8b80053a1 (\"ext4: fix race when reusing xattr\nblocks\")."
        }
      ],
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
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              "lang": "en",
              "value": "AV:N - The vulnerable ext4 xattr reuse path is reachable via VFS setxattr, and the same operations are driven remotely through in-kernel servers such as ksmbd and nfsd on an ext4-backed writable export, a reasonable severe deployment for file servers.\nAC:L - The attacker controls both sides of the race by issuing concurrent setxattr/removexattr operations that update e_reusable and e_referenced on a shared mbcache entry; creating ~1024 files with identical xattrs to reach REFCOUNT_MAX is also attacker-controlled.\nPR:N - In the most severe reasonable deployment, a guest/anonymous writable network export exposes create and xattr operations without real authentication; AUTH_SYS NFS UID spoofing similarly requires no privileged credentials.\nUI:N - The attacker triggers the bug directly by issuing filesystem requests; no separate victim action such as mounting a crafted image is required.\nS:U - The hang remains within the kernel/filesystem security authority with no VM escape, IOMMU bypass, or other cross-boundary impact.\nC:N - The bug only corrupts mbcache flag state into an inconsistent reusable/refcount combination; it does not disclose kernel or filesystem contents.\nI:N - There is no exploitable memory corruption or attacker-controlled data modification; the inconsistent flags only cause an infinite retry loop, not integrity compromise of stored data.\nA:H - ext4_xattr_block_set() loops indefinitely while holding a journal handle and inode xattr_sem, causing hung tasks and filesystem-wide denial of service; deadlock/infinite loop is high availability impact."
            }
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      "providerMetadata": {
        "dateUpdated": "2026-08-05T08:59:19.230Z",
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        "shortName": "Linux"
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      "title": "ext4: fix deadlock due to mbcache entry corruption",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2022-50668",
    "datePublished": "2025-12-09T01:29:19.526Z",
    "dateReserved": "2025-12-09T01:26:45.990Z",
    "dateUpdated": "2026-08-05T08:59:19.230Z",
    "state": "PUBLISHED"
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When this inconsistency happens, this\\ninconsistent state is kept indefinitely and so ext4_xattr_block_set()\\nkeeps retrying indefinitely.\\n\\nThe inconsistent state is caused by non-atomic update of e_reusable bit.\\ne_reusable is part of a bitfield and e_reusable update can race with\\nupdate of e_referenced bit in the same bitfield resulting in loss of one\\nof the updates. 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-04T19:37:31+00:00",
      "cve": "CVE-2022-50668",
      "id": "CVE-2022-50668",
      "initial_release_date": "2022-01-01T00:00:00+00:00",
      "product_status:fixed": "321",
      "product_status:known_affected": "52",
      "product_status:known_not_affected": "104",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ext4: fix deadlock due to mbcache entry corruption",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2022/cve-2022-50668.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-08-29T02:19:32Z",
      "cve": "CVE-2022-50668",
      "id": "CVE-2022-50668",
      "initial_release_date": "2025-12-10T00:38:24Z",
      "product_status:known_affected": "501",
      "product_status:known_not_affected": "213",
      "product_status:recommended": "284",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2022-50668",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2022-50668.json",
      "version": "40"
    }
  }
}



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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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  • 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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