Linux Kernel up to 5.4.119/5.10.37/5.11.21/5.12.4 sched uclamp off-by-one

Summaryinfo

A vulnerability described as problematic has been identified in Linux Kernel up to 5.4.119/5.10.37/5.11.21/5.12.4. Affected by this issue is the function uclamp of the component sched. The manipulation results in off-by-one. This vulnerability is identified as CVE-2021-46993. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Linux Kernel up to 5.4.119/5.10.37/5.11.21/5.12.4 (Operating System). Affected is the function uclamp of the component sched. The manipulation with an unknown input leads to a off-by-one vulnerability. CWE is classifying the issue as CWE-193. A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value. The impact remains unknown. CVE summarizes:

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.

The weakness was released 02/28/2024. The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2021-46993 since 02/27/2024. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 276021 (TencentOS Server 3: kernel (TSSA-2025:0434)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.4.120, 5.10.38, 5.11.22, 5.12.5 or 5.13 eliminates this vulnerability. Applying the patch 687f523c134b/f7347c85490b/3da3f804b82a/42ee47c7e356/6d2f8909a5fa is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (276021). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.4.119
• 5.10.0
• 5.10.1
• 5.10.2
• 5.10.3
• 5.10.4
• 5.10.5
• 5.10.6
• 5.10.7
• 5.10.8
• 5.10.9
• 5.10.10
• 5.10.11
• 5.10.12
• 5.10.13
• 5.10.14
• 5.10.15
• 5.10.16
• 5.10.17
• 5.10.18
• 5.10.19
• 5.10.20
• 5.10.21
• 5.10.22
• 5.10.23
• 5.10.24
• 5.10.25
• 5.10.26
• 5.10.27
• 5.10.28
• 5.10.29
• 5.10.30
• 5.10.31
• 5.10.32
• 5.10.33
• 5.10.34
• 5.10.35
• 5.10.36
• 5.10.37
• 5.11.0
• 5.11.1
• 5.11.2
• 5.11.3
• 5.11.4
• 5.11.5
• 5.11.6
• 5.11.7
• 5.11.8
• 5.11.9
• 5.11.10
• 5.11.11
• 5.11.12
• 5.11.13
• 5.11.14
• 5.11.15
• 5.11.16
• 5.11.17
• 5.11.18
• 5.11.19
• 5.11.20
• 5.11.21
• 5.12.0
• 5.12.1
• 5.12.2
• 5.12.3
• 5.12.4

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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Entryinfo

Once again VulDB remains the best source for vulnerability data.

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