Patch "KVM: s390: fix sthyi error handling" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    KVM: s390: fix sthyi error handling

to the 4.19-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-sthyi-error-handling.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 1da2e338737e83c3069b097f2674c18a36aed0f7
Author: Heiko Carstens <hca@xxxxxxxxxxxxx>
Date:   Thu Jul 27 20:29:39 2023 +0200

    KVM: s390: fix sthyi error handling
    
    [ Upstream commit 0c02cc576eac161601927b41634f80bfd55bfa9e ]
    
    Commit 9fb6c9b3fea1 ("s390/sthyi: add cache to store hypervisor info")
    added cache handling for store hypervisor info. This also changed the
    possible return code for sthyi_fill().
    
    Instead of only returning a condition code like the sthyi instruction would
    do, it can now also return a negative error value (-ENOMEM). handle_styhi()
    was not changed accordingly. In case of an error, the negative error value
    would incorrectly injected into the guest PSW.
    
    Add proper error handling to prevent this, and update the comment which
    describes the possible return values of sthyi_fill().
    
    Fixes: 9fb6c9b3fea1 ("s390/sthyi: add cache to store hypervisor info")
    Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230727182939.2050744-1-hca@xxxxxxxxxxxxx
    Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/s390/kernel/sthyi.c b/arch/s390/kernel/sthyi.c
index 888cc2f166db7..ce6084e28d904 100644
--- a/arch/s390/kernel/sthyi.c
+++ b/arch/s390/kernel/sthyi.c
@@ -460,9 +460,9 @@ static int sthyi_update_cache(u64 *rc)
  *
  * Fills the destination with system information returned by the STHYI
  * instruction. The data is generated by emulation or execution of STHYI,
- * if available. The return value is the condition code that would be
- * returned, the rc parameter is the return code which is passed in
- * register R2 + 1.
+ * if available. The return value is either a negative error value or
+ * the condition code that would be returned, the rc parameter is the
+ * return code which is passed in register R2 + 1.
  */
 int sthyi_fill(void *dst, u64 *rc)
 {
diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index a389fa85cca2d..5450d43d26ea5 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -360,8 +360,8 @@ static int handle_partial_execution(struct kvm_vcpu *vcpu)
  */
 int handle_sthyi(struct kvm_vcpu *vcpu)
 {
-	int reg1, reg2, r = 0;
-	u64 code, addr, cc = 0, rc = 0;
+	int reg1, reg2, cc = 0, r = 0;
+	u64 code, addr, rc = 0;
 	struct sthyi_sctns *sctns = NULL;
 
 	if (!test_kvm_facility(vcpu->kvm, 74))
@@ -392,7 +392,10 @@ int handle_sthyi(struct kvm_vcpu *vcpu)
 		return -ENOMEM;
 
 	cc = sthyi_fill(sctns, &rc);
-
+	if (cc < 0) {
+		free_page((unsigned long)sctns);
+		return cc;
+	}
 out:
 	if (!cc) {
 		r = write_guest(vcpu, addr, reg2, sctns, PAGE_SIZE);