From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Thu, 21 Dec 2017 08:18:22 +0000 (+0100)
Subject: KVM: s390: prevent buffer overrun on memory hotplug during migration
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=77bbeea7811f0857952d3f096438ce2e1bb16f1a;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

KVM: s390: prevent buffer overrun on memory hotplug during migration

commit c2cf265d860882b51a200e4a7553c17827f2b730 upstream.

We must not go beyond the pre-allocated buffer. This can happen when
a new memory slot is added during migration.

Reported-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Fixes: 190df4a212a7 (KVM: s390: CMMA tracking, ESSA emulation, migration mode)
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 5b25287f449b..7bd3a59232f0 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -1009,7 +1009,7 @@ static inline int do_essa(struct kvm_vcpu *vcpu, const int orc)
 		cbrlo[entries] = gfn << PAGE_SHIFT;
 	}
 
-	if (orc) {
+	if (orc && gfn < ms->bitmap_size) {
 		/* increment only if we are really flipping the bit to 1 */
 		if (!test_and_set_bit(gfn, ms->pgste_bitmap))
 			atomic64_inc(&ms->dirty_pages);