CVE-2021-47221

2024-05-2115:15:11

416baaa9-dc9f-4396-8d5f-8c081fb06d67

web.nvd.nist.gov

linux kernel

slub

redzoning

6.6 Medium

AI Score

Confidence

Low

0.0004 Low

EPSS

Percentile

15.6%

JSON

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.)

Affected configurations

Vulners

Node

linuxlinux_kernelRange5.7–5.10.46

linuxlinux_kernelRange5.11.0–5.12.13

linuxlinux_kernelRange5.13.0≥

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "mm/slub.c"
    ],
    "versions": [
      {
        "version": "89b83f282d8b",
        "lessThan": "f6ed23575416",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "89b83f282d8b",
        "lessThan": "ce6e8bee7a38",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "89b83f282d8b",
        "lessThan": "e41a49fadbc8",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "mm/slub.c"
    ],
    "versions": [
      {
        "version": "5.7",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "5.7",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.46",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.12.13",
        "lessThanOrEqual": "5.12.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.13",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]