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GHSA-3C4W-P6CR-WGQ6

Vulnerability from github – Published: 2024-05-21 15:31 – Updated: 2025-04-29 21:31

Details

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

mm/slub: actually fix freelist pointer vs redzoning

It turns out that SLUB redzoning ("slub_debug=Z") checks from s->object_size rather than from s->inuse (which is normally bumped to make room for the freelist pointer), so a cache created with an object size less than 24 would have the freelist pointer written beyond s->object_size, causing the redzone to be corrupted by the freelist pointer. This was very visible with "slub_debug=ZF":

BUG test (Tainted: G B ): Right Redzone overwritten

INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200 INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620

Redzone (_ptrval_): bb bb bb bb bb bb bb bb ........ Object (_ptrval_): 00 00 00 00 00 f6 f4 a5 ........ Redzone (_ptrval_): 40 1d e8 1a aa @.... Padding (_ptrval_): 00 00 00 00 00 00 00 00 ........

Adjust the offset to stay within s->object_size.

(Note that no caches of in this size range are known to exist in the kernel currently.)

Severity

5.5 (Medium)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2021-47221"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-763"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-05-21T15:15:11Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/slub: actually fix freelist pointer vs redzoning\n\nIt turns out that SLUB redzoning (\"slub_debug=Z\") checks from\ns-\u003eobject_size rather than from s-\u003einuse (which is normally bumped to\nmake room for the freelist pointer), so a cache created with an object\nsize less than 24 would have the freelist pointer written beyond\ns-\u003eobject_size, causing the redzone to be corrupted by the freelist\npointer.  This was very visible with \"slub_debug=ZF\":\n\n  BUG test (Tainted: G    B            ): Right Redzone overwritten\n  -----------------------------------------------------------------------------\n\n  INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb\n  INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200\n  INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620\n\n  Redzone  (____ptrval____): bb bb bb bb bb bb bb bb               ........\n  Object   (____ptrval____): 00 00 00 00 00 f6 f4 a5               ........\n  Redzone  (____ptrval____): 40 1d e8 1a aa                        @....\n  Padding  (____ptrval____): 00 00 00 00 00 00 00 00               ........\n\nAdjust the offset to stay within s-\u003eobject_size.\n\n(Note that no caches of in this size range are known to exist in the\nkernel currently.)",
  "id": "GHSA-3c4w-p6cr-wgq6",
  "modified": "2025-04-29T21:31:31Z",
  "published": "2024-05-21T15:31:39Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-47221"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ce6e8bee7a3883e8008b30f5887dbb426aac6a35"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e"
    },
    {
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  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2021-47221 (GCVE-0-2021-47221)

Vulnerability from cvelistv5 – Published: 2024-05-21 14:19 – Updated: 2026-05-11 13:50

Title

mm/slub: actually fix freelist pointer vs redzoning

Summary

In the Linux kernel, the following vulnerability has been resolved: mm/slub: actually fix freelist pointer vs redzoning It turns out that SLUB redzoning ("slub_debug=Z") checks from s->object_size rather than from s->inuse (which is normally bumped to make room for the freelist pointer), so a cache created with an object size less than 24 would have the freelist pointer written beyond s->object_size, causing the redzone to be corrupted by the freelist pointer. This was very visible with "slub_debug=ZF": BUG test (Tainted: G B ): Right Redzone overwritten ----------------------------------------------------------------------------- INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200 INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620 Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........ Object (____ptrval____): 00 00 00 00 00 f6 f4 a5 ........ Redzone (____ptrval____): 40 1d e8 1a aa @.... Padding (____ptrval____): 00 00 00 00 00 00 00 00 ........ Adjust the offset to stay within s->object_size. (Note that no caches of in this size range are known to exist in the kernel currently.)

Severity

No CVSS data available.

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2024-06-17 17:38 UTC

Assigner

Linux mitre root Scorecard

References

3 references

URL	Tags
https://git.kernel.org/stable/c/f6ed2357541612a13…
https://git.kernel.org/stable/c/ce6e8bee7a3883e80…
https://git.kernel.org/stable/c/e41a49fadbc80b60b…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 89b83f282d8ba380cf2124f88106c57df49c538c , < f6ed2357541612a13a5841b3af4dc32ed984a25f (git) Affected: 89b83f282d8ba380cf2124f88106c57df49c538c , < ce6e8bee7a3883e8008b30f5887dbb426aac6a35 (git) Affected: 89b83f282d8ba380cf2124f88106c57df49c538c , < e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e (git)
Linux	Linux	Affected: 5.7 Unaffected: 0 , < 5.7 (semver) Unaffected: 5.10.46 , ≤ 5.10.* (semver) Unaffected: 5.12.13 , ≤ 5.12.* (semver) Unaffected: 5.13 , ≤ * (original_commit_for_fix)

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Sightings

Author	Source	Type	Date	Other

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.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
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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GHSA-3C4W-P6CR-WGQ6

CVE-2021-47221 (GCVE-0-2021-47221)

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