CVE-2021-46993 sched: Fix out-of-bound access in uclamp

2024-02-2808:13:18

Linux

www.cve.org

vulnerability

linux kernel

sched

uclamp

out-of-bound access

performance issue

memory access

8.6 High

AI Score

Confidence

High

0.0004 Low

EPSS

Percentile

15.7%

JSON

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

sched: Fix out-of-bound access in uclamp

Util-clamp places tasks in different buckets based on their clamp values
for performance reasons. However, the size of buckets is currently
computed using a rounding division, which can lead to an off-by-one
error in some configurations.

For instance, with 20 buckets, the bucket size will be 1024/20=51. A
task with a clamp of 1024 will be mapped to bucket id 1024/51=20. Sadly,
correct indexes are in range [0,19], hence leading to an out of bound
memory access.

Clamp the bucket id to fix the issue.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "kernel/sched/core.c"
    ],
    "versions": [
      {
        "version": "69842cba9ace",
        "lessThan": "687f523c134b",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "69842cba9ace",
        "lessThan": "f7347c85490b",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "69842cba9ace",
        "lessThan": "3da3f804b82a",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "69842cba9ace",
        "lessThan": "42ee47c7e356",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "69842cba9ace",
        "lessThan": "6d2f8909a5fa",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "kernel/sched/core.c"
    ],
    "versions": [
      {
        "version": "5.3",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "5.3",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.120",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.38",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.11.22",
        "lessThanOrEqual": "5.11.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.12.5",
        "lessThanOrEqual": "5.12.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.13",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]