CVE-2025-21694: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: fs/proc: fix softlockup in __read_vmcore (part 2) Since commit 5cbcb62dddf5 ("fs/proc: fix softlockup in __read_vmcore") the number of softlockups in __read_vmcore at kdump time have gone down, but they still happen sometimes. In a memory constrained environment like the kdump image, a softlockup is not just a harmless message, but it can interfere with things like RCU freeing memory, causing the crashdump to get stuck. The second loop in __read_vmcore has a lot more opportunities for natural sleep points, like scheduling out while waiting for a data write to happen, but apparently that is not always enough. Add a cond_resched() to the second loop in __read_vmcore to (hopefully) get rid of the softlockups.

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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	4.19.317 — 4.20
linux	linux_kernel	5.4.279 — 5.4.290
linux	linux_kernel	5.10.221 — 5.10.234
linux	linux_kernel	5.15.162 — 5.15.177
linux	linux_kernel	6.1.95 — 6.1.127
linux	linux_kernel	6.6.35 — 6.6.74
linux	linux_kernel	6.9.6 — 6.12.11
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/649b266606bc413407ce315f710c8ce8a88ee30a https://git.kernel.org/stable/c/65c367bd9d4f43513c7f837df5753bea9561b836 https://git.kernel.org/stable/c/80828540dad0757b6337c6561d49c81038f38d87 https://git.kernel.org/stable/c/80da29deb88a3a907441fc35bb7bac309f31e713 https://git.kernel.org/stable/c/84c4ed15626574c9ac6c1039ba9c137a77bcc7f2 https://git.kernel.org/stable/c/a5a2ee8144c3897d37403a69118c3e3dc5713958 https://git.kernel.org/stable/c/cbc5dde0a461240046e8a41c43d7c3b76d5db952

Other References

https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html https://cert-portal.siemens.com/productcert/html/ssa-265688.html https://cert-portal.siemens.com/productcert/html/ssa-355557.html https://cert-portal.siemens.com/productcert/html/ssa-398330.html

Frequently Asked Questions

What is CVE-2025-21694? +

In the Linux kernel, the following vulnerability has been resolved: fs/proc: fix softlockup in __read_vmcore (part 2) Since commit 5cbcb62dddf5 ("fs/proc: fix softlockup in __read_vmcore") the number of softlockups in __read_vmcore at kdump time have gone down, but they still happen sometimes. In a memory constrained environment like the kdump image, a softlockup is not just a harmless message, but it can interfere with things like RCU freeing memory, causing the crashdump to get stuck. The second loop in __read_vmcore has a lot more opportunities for natural sleep points, like scheduling out while waiting for a data write to happen, but apparently that is not always enough. Add a cond_resched() to the second loop in __read_vmcore to (hopefully) get rid of the softlockups. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-21694? +

CVE-2025-21694 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-2025-21694? +

CVE-2025-21694 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-2025-21694? +

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-2025-21694