Bug 2345243 (CVE-2025-21694)

Summary: CVE-2025-21694 kernel: fs/proc: fix softlockup in __read_vmcore (part 2)
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
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Hardware: All   
OS: Linux   
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Description OSIDB Bzimport 2025-02-12 14:10:06 UTC 
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.
Comment 1 Robb Gatica 2025-02-12 20:31:58 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025021259-CVE-2025-21694-f5ca@gregkh/T
Comment 4 errata-xmlrpc 2025-05-13 08:39:12 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2025:6966 https://access.redhat.com/errata/RHSA-2025:6966