KVM: s390: Fix kvm_s390_vcpu_unsetup_cmma()

In some cases kvm_s390_vcpu_unsetup_cmma() can be called with a 0
cbrlo; in such cases, if running with V != R, free_page() will attempt
to free physical page 0.

Fix by freeing cbrlo only if it's non-zero.

Fixes: b31605c12f4e ("KVM: s390: make cmma usage conditionally")
Fixes: 29b40f105ec8 ("KVM: s390: protvirt: Add initial vm and cpu lifecycle handling")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260803124040.126471-4-imbrenda@linux.ibm.com>

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 1b3290a5ad1aee1c616feec456ce49a5b6b3ab75..9be27db0a21e628f7bb7a1891a56232543769aec 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -3678,7 +3678,8 @@ static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu)
 
 void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu)
 {
-       free_page((unsigned long)phys_to_virt(vcpu->arch.sie_block->cbrlo));
+       if (vcpu->arch.sie_block->cbrlo)
+               free_page((unsigned long)phys_to_virt(vcpu->arch.sie_block->cbrlo));
        vcpu->arch.sie_block->cbrlo = 0;
 }