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Review reviewHigh

CVE-2021-46984

Linux Linux, linux kernel

In the Linux kernel, the following vulnerability has been resolved: kyber: fix out of bounds access when preempted __blk_mq_sched_bio_merge() gets the ctx and hctx for the current CPU and passes the hctx to ->bio_merge(). kyber_bio_merge() then gets the ctx for the current CPU again and uses that to get the corresponding Kyber context in the passed hctx. However, the thread may be preempted between the two calls to blk_mq_get_ctx(), and the ctx returned the second time may no longer correspond to the passed hctx. This "works" accidentally most of the time, but it can cause us to read garbag...

CVSS
7.8
EPSS
0.26%
17.2% percentile
CISA KEV
Not listed
Published
2024.02.28
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.26%
Technical severityCVSS 7.8

Vulnerability overview

In the Linux kernel, the following vulnerability has been resolved: kyber: fix out of bounds access when preempted __blk_mq_sched_bio_merge() gets the ctx and hctx for the current CPU and passes the hctx to ->bio_merge(). kyber_bio_merge() then gets the ctx for the current CPU again and uses that to get the corresponding Kyber context in the passed hctx. However, the thread may be preempted between the two calls to blk_mq_get_ctx(), and the ctx returned the second time may no longer correspond to the passed hctx. This "works" accidentally most of the time, but it can cause us to read garbag...

Affected product and versions

Product
Linux Linux, linux kernel
Affected versions
>= a6088845c2bf754d6cb2572b484180680b037804 < 0b6b4b90b74c27bea968c214d820ba4254b903a5, >= a6088845c2bf754d6cb2572b484180680b037804 < 54dbe2d2c1fcabf650c7a8b747601da355cd7f9f, >= a6088845c2bf754d6cb2572b484180680b037804 < a287cd84e047045f5a4d4da793414e848de627c6, >= a6088845c2bf754d6cb2572b484180680b037804 < 2ef3c76540c49167a0bc3d5f80d00fd1fc4586df, >= a6088845c2bf754d6cb2572b484180680b037804 < efed9a3337e341bd0989161b97453b52567bc59d, >= 4.18, >= 4.18 < 5.4.120, >= 5.5 < 5.10.38, >= 5.11 < 5.11.22, >= 5.12 < 5.12.5, 5.13
Fixed versions
5.4.120, 5.10.38, 5.11.22, 5.12.5

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux Linux, linux kernel and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-129
CVE-2021-46984 — Linux Linux, linux kernel | SECUFOCUS NOW