linux-kernel - [PATCH 4.14 061/164] KVM: s390: Fix skey emulation permission check

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Date:   Tue, 12 Dec 2017 13:44:01 +0100
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>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Thomas Huth <thuth@...hat.com>
Subject: [PATCH 4.14 061/164] KVM: s390: Fix skey emulation permission check

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

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

From: Janosch Frank <frankja@...ux.vnet.ibm.com>

commit ca76ec9ca871e67d8cd0b6caba24aca3d3ac4546 upstream.

All skey functions call skey_check_enable at their start, which checks
if we are in the PSTATE and injects a privileged operation exception
if we are.

Unfortunately they continue processing afterwards and perform the
operation anyhow as skey_check_enable does not deliver an error if the
exception injection was successful.

Let's move the PSTATE check into the skey functions and exit them on
such an occasion, also we now do not enable skey handling anymore in
such a case.

Signed-off-by: Janosch Frank <frankja@...ux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@...ibm.com>
Fixes: a7e19ab ("KVM: s390: handle missing storage-key facility")
Reviewed-by: Cornelia Huck <cohuck@...hat.com>
Reviewed-by: Thomas Huth <thuth@...hat.com>
Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/s390/kvm/priv.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -235,8 +235,6 @@ static int try_handle_skey(struct kvm_vc
 		VCPU_EVENT(vcpu, 4, "%s", "retrying storage key operation");
 		return -EAGAIN;
 	}
-	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
-		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
 	return 0;
 }
 
@@ -247,6 +245,9 @@ static int handle_iske(struct kvm_vcpu *
 	int reg1, reg2;
 	int rc;
 
+	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
+		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
+
 	rc = try_handle_skey(vcpu);
 	if (rc)
 		return rc != -EAGAIN ? rc : 0;
@@ -276,6 +277,9 @@ static int handle_rrbe(struct kvm_vcpu *
 	int reg1, reg2;
 	int rc;
 
+	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
+		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
+
 	rc = try_handle_skey(vcpu);
 	if (rc)
 		return rc != -EAGAIN ? rc : 0;
@@ -311,6 +315,9 @@ static int handle_sske(struct kvm_vcpu *
 	int reg1, reg2;
 	int rc;
 
+	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
+		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
+
 	rc = try_handle_skey(vcpu);
 	if (rc)
 		return rc != -EAGAIN ? rc : 0;