CVE-2021-47221 Affecting kernel-rt-kvm package, versions *


Severity

low

    Threat Intelligence

    EPSS
    0.05% (16th percentile)

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  • Snyk ID SNYK-CENTOS7-KERNELRTKVM-7113485
  • published 24 May 2024
  • disclosed 21 May 2024

Introduced: 21 May 2024

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How to fix?

There is no fixed version for Centos:7 kernel-rt-kvm.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-kvm package and not the kernel-rt-kvm package as distributed by Centos. See How to fix? for Centos:7 relevant fixed versions and status.

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.)

CVSS Scores

version 3.1
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Snyk

5.5 low
  • Attack Vector (AV)
    Local
  • Attack Complexity (AC)
    Low
  • Privileges Required (PR)
    Low
  • User Interaction (UI)
    None
  • Scope (S)
    Unchanged
  • Confidentiality (C)
    None
  • Integrity (I)
    None
  • Availability (A)
    High
Expand this section

Red Hat

5.5 medium