CVE-2021-47491: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: mm: khugepaged: skip huge page collapse for special files The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2]. This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface. [[email protected]: fix vm_file check [3]]

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.4 — 5.10.78
linux	linux_kernel	5.11 — 5.14.16
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/5fcb6fce74ffa614d964667110cf1a516c48c6d9 https://git.kernel.org/stable/c/6d67b2a73b8e3a079c355bab3c1aef7d85a044b8 https://git.kernel.org/stable/c/a4aeaa06d45e90f9b279f0b09de84bd00006e733 https://git.kernel.org/stable/c/5fcb6fce74ffa614d964667110cf1a516c48c6d9 https://git.kernel.org/stable/c/6d67b2a73b8e3a079c355bab3c1aef7d85a044b8 https://git.kernel.org/stable/c/a4aeaa06d45e90f9b279f0b09de84bd00006e733

Frequently Asked Questions

What is CVE-2021-47491? +

In the Linux kernel, the following vulnerability has been resolved: mm: khugepaged: skip huge page collapse for special files The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2]. This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface. [[email protected]: fix vm_file check [3]] It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-47491? +

CVE-2021-47491 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2021-47491? +

CVE-2021-47491 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2021-47491? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2021-47491