From: Claudio Imbrenda <imbrenda@linux.ibm.com>
Date: Thu, 2 Apr 2026 15:01:35 +0000 (+0200)
Subject: KVM: s390: ucontrol: Fix memslot handling
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9b8e8aad5896d66005d29920cb1643076a20b172;p=thirdparty%2Fkernel%2Flinux.git

KVM: s390: ucontrol: Fix memslot handling

Fix memslots handling for UCONTROL guests. Attempts to delete user
memslots will fail, as they should, without the risk of a NULL pointer
dereference.

Fixes: 413c98f24c63 ("KVM: s390: fake memslot for ucontrol VMs")
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 156878c95e067..63bc496d0c37e 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -5642,7 +5642,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				   struct kvm_memory_slot *new,
 				   enum kvm_mr_change change)
 {
-	if (kvm_is_ucontrol(kvm) && new->id < KVM_USER_MEM_SLOTS)
+	if (kvm_is_ucontrol(kvm) && new && new->id < KVM_USER_MEM_SLOTS)
 		return -EINVAL;
 
 	/* When we are protected, we should not change the memory slots */