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authorHeiko Carstens <heiko.carstens@de.ibm.com>2017-08-03 13:05:40 +0200
committerChristian Borntraeger <borntraeger@de.ibm.com>2017-08-29 15:15:56 +0200
commit631aebfee8261d66597ce0f88ba046c77a0e415e (patch)
treeeede4dee7ce0db5beeba074cceff099a38eee01a /arch/s390/kvm/sthyi.c
parentKVM: s390: Multiple Epoch Facility support (diff)
downloadlinux-631aebfee8261d66597ce0f88ba046c77a0e415e.tar.xz
linux-631aebfee8261d66597ce0f88ba046c77a0e415e.zip
KVM: s390: sthyi: remove invalid guest write access
handle_sthyi() always writes to guest memory if the sthyi function code is zero in order to fault in the page that later is written to. However a function code of zero does not necessarily mean that a write to guest memory happens: if the KVM host is running as a second level guest under z/VM 6.2 the sthyi instruction is indicated to be available to the KVM host, however if the instruction is executed it will always return with a return code that indicates "unsupported function code". In such a case handle_sthyi() must not write to guest memory. This means that the prior write access to fault in the guest page may result in invalid guest exceptions, and/or invalid data modification. In order to be architecture compliant simply remove the write_guest() call. Given that the guest assumed a write access anyway, this fix does not qualify for -stable. This just makes sure the sthyi handler is architecture compliant. Fixes: 95ca2cb57985 ("KVM: s390: Add sthyi emulation") Reviewed-by: Janosch Frank <frankja@linux.vnet.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Diffstat (limited to 'arch/s390/kvm/sthyi.c')
-rw-r--r--arch/s390/kvm/sthyi.c8
1 files changed, 0 insertions, 8 deletions
diff --git a/arch/s390/kvm/sthyi.c b/arch/s390/kvm/sthyi.c
index a2e5c24f47a7..395926b8c1ed 100644
--- a/arch/s390/kvm/sthyi.c
+++ b/arch/s390/kvm/sthyi.c
@@ -436,14 +436,6 @@ int handle_sthyi(struct kvm_vcpu *vcpu)
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.
- */
- r = write_guest(vcpu, addr, reg2, &cc, 1);
- if (r)
- return kvm_s390_inject_prog_cond(vcpu, r);
-
sctns = (void *)get_zeroed_page(GFP_KERNEL);
if (!sctns)
return -ENOMEM;