| From 3e6fcb7bc41cd4b546e1f61174cf380a3d9acada Mon Sep 17 00:00:00 2001 |
| From: Thomas Huth <thuth@redhat.com> |
| Date: Thu, 29 Aug 2019 14:25:17 +0200 |
| Subject: [PATCH] KVM: s390: Test for bad access register and size at the start |
| of S390_MEM_OP |
| |
| commit a13b03bbb4575b350b46090af4dfd30e735aaed1 upstream. |
| |
| If the KVM_S390_MEM_OP ioctl is called with an access register >= 16, |
| then there is certainly a bug in the calling userspace application. |
| We check for wrong access registers, but only if the vCPU was already |
| in the access register mode before (i.e. the SIE block has recorded |
| it). The check is also buried somewhere deep in the calling chain (in |
| the function ar_translation()), so this is somewhat hard to find. |
| |
| It's better to always report an error to the userspace in case this |
| field is set wrong, and it's safer in the KVM code if we block wrong |
| values here early instead of relying on a check somewhere deep down |
| the calling chain, so let's add another check to kvm_s390_guest_mem_op() |
| directly. |
| |
| We also should check that the "size" is non-zero here (thanks to Janosch |
| Frank for the hint!). If we do not check the size, we could call vmalloc() |
| with this 0 value, and this will cause a kernel warning. |
| |
| Signed-off-by: Thomas Huth <thuth@redhat.com> |
| Link: https://lkml.kernel.org/r/20190829122517.31042-1-thuth@redhat.com |
| Reviewed-by: Cornelia Huck <cohuck@redhat.com> |
| Reviewed-by: Janosch Frank <frankja@linux.ibm.com> |
| Reviewed-by: David Hildenbrand <david@redhat.com> |
| Cc: stable@vger.kernel.org |
| Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c |
| index 4934141689d2..db64187e9505 100644 |
| --- a/arch/s390/kvm/kvm-s390.c |
| +++ b/arch/s390/kvm/kvm-s390.c |
| @@ -4259,7 +4259,7 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu, |
| const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION |
| | KVM_S390_MEMOP_F_CHECK_ONLY; |
| |
| - if (mop->flags & ~supported_flags) |
| + if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size) |
| return -EINVAL; |
| |
| if (mop->size > MEM_OP_MAX_SIZE) |
| -- |
| 2.7.4 |
| |