[PATCH v2 8/9] KVM: s390: Fix potential tiny kernel stack leak

[Claudio Imbrenda]

In some circumstances, one bit of kernel stack could have been leaked
from dat_cond_set_storage_key().

Fix by clearing prev before use.

Fixes: 8e03e8316eb2 ("KVM: s390: KVM page table management functions: storage keys")
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
---
 arch/s390/kvm/dat.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/s390/kvm/dat.c b/arch/s390/kvm/dat.c
index f4dd6f783417..f2ea013cb33e 100644
--- a/arch/s390/kvm/dat.c
+++ b/arch/s390/kvm/dat.c
@@ -737,6 +737,7 @@ int dat_cond_set_storage_key(struct kvm_s390_mmu_cache *mmc, union asce asce, gf
 	pgste.fp = skey.fp;
 	pgste.gc = skey.c;
 	pgste.gr = skey.r;
+	prev.skey = 0;
 
 	if (!ptep->h.i) {
 		rc = page_cond_set_storage_key(pte_origin(*ptep), skey, &prev, nq, mr, mc);
-- 
2.55.0