FAILED: patch "[PATCH] KVM: s390: Zero initialize data structures for" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 4e2c7f7cbc27418f9a290399b986c1b85ff93b90
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090923-freestyle-whacking-e0e0@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 4e2c7f7cbc27418f9a290399b986c1b85ff93b90 Mon Sep 17 00:00:00 2001
From: Christian Borntraeger <[email protected]>
Date: Wed, 5 Aug 2026 13:04:49 +0200
Subject: [PATCH] KVM: s390: Zero initialize data structures for
inject_pfault_token

__kvm_inject_pfault_token() only sets .type and .u.ext.ext_params2 of the on-stack struct kvm_s390_irq but the full ext substructure is copied into the cpu local variable on inject. ext_params and pad contain stale stack values.

Interrupt delivery only uses ext_params2, so nothing leaks to the guest, but a host user can use the migration ioctls to get to the data.

Fix by zero-initializing the irq struct.
Do the same for the inti data structure.

Message-ID: <[email protected]>

index 518a69c55e85..611dcb534210 100644
@@ -4474,8 +4474,8 @@ int kvm_s390_try_set_tod_clock(struct kvm *kvm, const struct kvm_s390_vm_tod_clo
 static void __kvm_inject_pfault_token(struct kvm_vcpu *vcpu, bool start_token,
 				     unsigned long token)
 {
-	struct kvm_s390_interrupt inti;
-	struct kvm_s390_irq irq;
+	struct kvm_s390_interrupt inti = {};
+	struct kvm_s390_irq irq = {};
 	struct kvm_s390_interrupt_info *inti_mem = NULL;
 	int ret = 0;
 

From: Christian Borntraeger <[email protected]>

[ Upstream commit 4e2c7f7cbc27418f9a290399b986c1b85ff93b90 ]

__kvm_inject_pfault_token() only sets .type and .u.ext.ext_params2 of the on-stack struct kvm_s390_irq but the full ext substructure is copied into the cpu local variable on inject. ext_params and pad contain stale stack values.

Interrupt delivery only uses ext_params2, so nothing leaks to the guest, but a host user can use the migration ioctls to get to the data.

Fix by zero-initializing the irq struct.
Do the same for the inti data structure.

Message-ID: <[email protected]>

---
 arch/s390/kvm/kvm-s390.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index 8b31d482712fe..ed08e2f3a8ec5 100644
@@ -4705,8 +4705,8 @@ int kvm_s390_try_set_tod_clock(struct kvm *kvm, const struct kvm_s390_vm_tod_clo
 static void __kvm_inject_pfault_token(struct kvm_vcpu *vcpu, bool start_token,
 				      unsigned long token)
 {
-	struct kvm_s390_interrupt inti;
-	struct kvm_s390_irq irq;
+	struct kvm_s390_interrupt inti = {};
+	struct kvm_s390_irq irq = {};
 
 	if (start_token) {
 		irq.u.ext.ext_params2 = token;

2.53.0