linux-kernel - [PATCH 4.9 31/84] KVM: s390: sthyi: fix specification exception detection

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Date:   Mon, 28 Aug 2017 10:04:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Janosch Frank <frankja@...ux.vnet.ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
Subject: [PATCH 4.9 31/84] KVM: s390: sthyi: fix specification exception detection

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Heiko Carstens <heiko.carstens@...ibm.com>

commit 857b8de96795646c5891cf44ae6fb19b9ff74bf9 upstream.

sthyi should only generate a specification exception if the function
code is zero and the response buffer is not on a 4k boundary.

The current code would also test for unknown function codes if the
response buffer, that is currently only defined for function code 0,
is not on a 4k boundary and incorrectly inject a specification
exception instead of returning with condition code 3 and return code 4
(unsupported function code).

Fix this by moving the boundary check.

Fixes: 95ca2cb57985 ("KVM: s390: Add sthyi emulation")
Reviewed-by: Janosch Frank <frankja@...ux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
Reviewed-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Cornelia Huck <cohuck@...hat.com>
Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/s390/kvm/sthyi.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/arch/s390/kvm/sthyi.c
+++ b/arch/s390/kvm/sthyi.c
@@ -422,7 +422,7 @@ int handle_sthyi(struct kvm_vcpu *vcpu)
 	VCPU_EVENT(vcpu, 3, "STHYI: fc: %llu addr: 0x%016llx", code, addr);
 	trace_kvm_s390_handle_sthyi(vcpu, code, addr);
 
-	if (reg1 == reg2 || reg1 & 1 || reg2 & 1 || addr & ~PAGE_MASK)
+	if (reg1 == reg2 || reg1 & 1 || reg2 & 1)
 		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
 
 	if (code & 0xffff) {
@@ -430,6 +430,9 @@ int handle_sthyi(struct kvm_vcpu *vcpu)
 		goto out;
 	}
 
+	if (addr & ~PAGE_MASK)
+		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
+
 	/*
 	 * If the page has not yet been faulted in, we want to do that
 	 * now and not after all the expensive calculations.