CVE-2026-89922: KVM: s390: Take srcu when importing watchpoint data

CVE-2026-89922: KVM: s390: Take srcu when importing watchpoint data

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

KVM: s390: Take srcu when importing watchpoint data

__import_wp_info() backs up the original guest memory contents of a
watchpoint with read_guest_abs(), which is kvm_read_guest() and therefore
resolves the memslot via __kvm_memslots(). That requires kvm->srcu (or
kvm->slots_lock) to be held, otherwise a concurrent memslot update can
free the memslots array under us once its SRCU grace period has elapsed.

As this is not fast path, following lock ordering (mutex first, then
srcu) take the big hammer and hold the srcu for the full import.

The Linux kernel CVE team has assigned CVE-2026-89922 to this issue.


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

	Issue introduced in 3.16 with commit 27291e2165b6de70c476b7b675308113edd69a60 and fixed in 6.1.188 with commit 6830fbc3724bf49c142aae69a4694f115fa9cedd
	Issue introduced in 3.16 with commit 27291e2165b6de70c476b7b675308113edd69a60 and fixed in 6.6.157 with commit f8e3a9997d5ecd56ebe4b262ff424516c068fecb
	Issue introduced in 3.16 with commit 27291e2165b6de70c476b7b675308113edd69a60 and fixed in 6.12.110 with commit 76f5b4ea9ed0aa5a34bda9d8a878f2c73026ec03
	Issue introduced in 3.16 with commit 27291e2165b6de70c476b7b675308113edd69a60 and fixed in 6.18.51 with commit cc710ee45395efb4937e042960f791d33924e5f6
	Issue introduced in 3.16 with commit 27291e2165b6de70c476b7b675308113edd69a60 and fixed in 7.2.5 with commit 4c05bf21d1806853e662cc19e744736a3408f155
	Issue introduced in 3.16 with commit 27291e2165b6de70c476b7b675308113edd69a60 and fixed in 7.3-rc1 with commit a4e482def8533ebace517d9f67f1465841b1f982

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-2026-89922
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:
	arch/s390/kvm/kvm-s390.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/6830fbc3724bf49c142aae69a4694f115fa9cedd
	https://git.kernel.org/stable/c/f8e3a9997d5ecd56ebe4b262ff424516c068fecb
	https://git.kernel.org/stable/c/76f5b4ea9ed0aa5a34bda9d8a878f2c73026ec03
	https://git.kernel.org/stable/c/cc710ee45395efb4937e042960f791d33924e5f6
	https://git.kernel.org/stable/c/4c05bf21d1806853e662cc19e744736a3408f155
	https://git.kernel.org/stable/c/a4e482def8533ebace517d9f67f1465841b1f982