linux-cve-announce - CVE-2025-21694: fs/proc: fix softlockup in __read

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Message-ID: <2025021259-CVE-2025-21694-f5ca@gregkh>
Date: Wed, 12 Feb 2025 14:26:58 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21694: fs/proc: fix softlockup in __read_vmcore (part 2)

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.

The Linux kernel CVE team has assigned CVE-2025-21694 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.4.279 with commit 803d5a33d5ffdc2d86dcc0cfa01655a330612cdb and fixed in 5.4.290 with commit 84c4ed15626574c9ac6c1039ba9c137a77bcc7f2
	Issue introduced in 5.10.221 with commit 70c1835e776c8447c1aca87ddb38cfe764fe756a and fixed in 5.10.234 with commit 80da29deb88a3a907441fc35bb7bac309f31e713
	Issue introduced in 5.15.162 with commit e1b160a50c756e0efbea290b9bf5117cb80e8c4b and fixed in 5.15.177 with commit 649b266606bc413407ce315f710c8ce8a88ee30a
	Issue introduced in 6.1.95 with commit a373ad833a6bfe4bc6cedcf7e56a99cc6fd9a193 and fixed in 6.1.127 with commit 65c367bd9d4f43513c7f837df5753bea9561b836
	Issue introduced in 6.6.35 with commit 518fbd644dabb6aedbdd4939c6c9cc1bf651459f and fixed in 6.6.74 with commit a5a2ee8144c3897d37403a69118c3e3dc5713958
	Issue introduced in 6.10 with commit 5cbcb62dddf5346077feb82b7b0c9254222d3445 and fixed in 6.12.11 with commit 80828540dad0757b6337c6561d49c81038f38d87
	Issue introduced in 6.10 with commit 5cbcb62dddf5346077feb82b7b0c9254222d3445 and fixed in 6.13 with commit cbc5dde0a461240046e8a41c43d7c3b76d5db952
	Issue introduced in 4.19.317 with commit 7bdf1d550ddfcd9ab797087421f77b7aceddc8a7
	Issue introduced in 6.9.6 with commit e8780e8a0e25dc4c3927f611ec8970d26c0c7369

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-21694
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/proc/vmcore.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/84c4ed15626574c9ac6c1039ba9c137a77bcc7f2
	https://git.kernel.org/stable/c/80da29deb88a3a907441fc35bb7bac309f31e713
	https://git.kernel.org/stable/c/649b266606bc413407ce315f710c8ce8a88ee30a
	https://git.kernel.org/stable/c/65c367bd9d4f43513c7f837df5753bea9561b836
	https://git.kernel.org/stable/c/a5a2ee8144c3897d37403a69118c3e3dc5713958
	https://git.kernel.org/stable/c/80828540dad0757b6337c6561d49c81038f38d87
	https://git.kernel.org/stable/c/cbc5dde0a461240046e8a41c43d7c3b76d5db952