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author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2017-08-03 13:05:40 +0200 |
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committer | Christian Borntraeger <borntraeger@de.ibm.com> | 2017-08-29 15:15:56 +0200 |
commit | 631aebfee8261d66597ce0f88ba046c77a0e415e (patch) | |
tree | eede4dee7ce0db5beeba074cceff099a38eee01a /arch | |
parent | KVM: s390: Multiple Epoch Facility support (diff) | |
download | linux-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')
-rw-r--r-- | arch/s390/kvm/sthyi.c | 8 |
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; |