Patch "KVM: s390: Fix skey emulation permission check" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

KVM: s390: Fix skey emulation permission check

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-s390-fix-skey-emulation-permission-check.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Janosch Frank <[email protected]>
Date: Mon, 4 Dec 2017 12:19:11 +0100
Subject: KVM: s390: Fix skey emulation permission check

From: Janosch Frank <[email protected]>

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.

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

@@ -197,8 +197,6 @@ 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;
 }
 

@@ -209,6 +207,9 @@ 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;

@@ -238,6 +239,9 @@ 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;

@@ -273,6 +277,9 @@ 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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/kvm-s390-fix-skey-emulation-permission-check.patch