linux-kernel - [PATCH v7 15/15] KVM: s390: fix possible null pointer dereference in pending

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Message-Id: <20190131085247.13826-16-mimu@linux.ibm.com>
Date:   Thu, 31 Jan 2019 09:52:46 +0100
From:   Michael Mueller <mimu@...ux.ibm.com>
To:     KVM Mailing List <kvm@...r.kernel.org>
Cc:     Linux-S390 Mailing List <linux-s390@...r.kernel.org>,
        linux-kernel@...r.kernel.org,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Pierre Morel <pmorel@...ux.ibm.com>,
        Michael Mueller <mimu@...ux.ibm.com>
Subject: [PATCH v7 15/15] KVM: s390: fix possible null pointer dereference in pending_irqs()

Assure a GISA is in use before accessing the IPM to avoid a
null pointer dereference issue.

Signed-off-by: Michael Mueller <mimu@...ux.ibm.com>
Reported-by: Halil Pasic <pasic@...ux.ibm.com>
---
 arch/s390/kvm/interrupt.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index d322400ca587..660ec87b6e60 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -329,9 +329,13 @@ static inline unsigned long pending_irqs_no_gisa(struct kvm_vcpu *vcpu)
 
 static inline unsigned long pending_irqs(struct kvm_vcpu *vcpu)
 {
-	return pending_irqs_no_gisa(vcpu) |
-		gisa_get_ipm(vcpu->kvm->arch.gisa_int.origin) <<
-			IRQ_PEND_IO_ISC_7;
+	struct kvm_s390_gisa_interrupt *gi = &vcpu->kvm->arch.gisa_int;
+	unsigned long pending_mask;
+
+	pending_mask = pending_irqs_no_gisa(vcpu);
+	if (gi->origin)
+		pending_mask |= gisa_get_ipm(gi->origin) << IRQ_PEND_IO_ISC_7;
+	return pending_mask;
 }
 
 static inline int isc_to_irq_type(unsigned long isc)
-- 
2.13.4