CVE-2026-98930: KVM: s390: Fix IRQ injection with SIGP Stop and Store Status

CVE-2026-98930: KVM: s390: Fix IRQ injection with SIGP Stop and Store Status

[Greg Kroah-Hartman]

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

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

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

KVM: s390: Fix IRQ injection with SIGP Stop and Store Status

When __inject_sigp_stop() is called for a Stop and Store Status
operation, if the vCPU is running, the interrupt is marked as pending
and the status is stored by the thread performing the KVM_RUN IOCTL.

If the vCPU is already stopped, the status is stored immediately.

Storing the status means writing into userspace, which might fault, and
__inject_sigp_stop() is called from do_inject_vcpu() which in turn is
always called holding a spinlock, which is obviously an issue.

Fix this by returning -EWOULDBLOCK from __inject_sigp_stop(), and
adding a bool flag to indicate whether a store status is needed. The
callers of do_inject_vcpu() are modified to pass the pointer to the
bool flag; whenever a Store Status operation is needed, the callers can
now perform it outside the spinlock.

Opportunistically refactor kvm_s390_set_irq_state() to use
scoped_guard() and __free().

[ Added Fixes tag while picking -- Claudio ]

The Linux kernel CVE team has assigned CVE-2026-98930 to this issue.


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

	Issue introduced in 4.0 with commit 6cddd432e3da5e25eccbc13844d03c871674a62e and fixed in 6.12.112 with commit 3bd77c59576b1d447fd56cc689ae9523a334b924
	Issue introduced in 4.0 with commit 6cddd432e3da5e25eccbc13844d03c871674a62e and fixed in 6.18.55 with commit a379ac504fcb8c6fc2aa36203f5489b9581eb2e0
	Issue introduced in 4.0 with commit 6cddd432e3da5e25eccbc13844d03c871674a62e and fixed in 7.2.9 with commit d0e3bf633f0585a0c2c2105ea7723777d764fae5
	Issue introduced in 4.0 with commit 6cddd432e3da5e25eccbc13844d03c871674a62e and fixed in 7.3 with commit d343407b728a80b74be3c24b59f15e60289ea527

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-2026-98930
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/interrupt.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/3bd77c59576b1d447fd56cc689ae9523a334b924
	https://git.kernel.org/stable/c/a379ac504fcb8c6fc2aa36203f5489b9581eb2e0
	https://git.kernel.org/stable/c/d0e3bf633f0585a0c2c2105ea7723777d764fae5
	https://git.kernel.org/stable/c/d343407b728a80b74be3c24b59f15e60289ea527