On 29.08.19 14:40, Cornelia Huck wrote: > On Thu, 29 Aug 2019 14:25:17 +0200 > Thomas Huth <thuth@xxxxxxxxxx> wrote: > >> 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@xxxxxxxxxx> I will add cc stable. Thanks applied. >> --- >> v2: Check mop->size to be non-zero >> >> arch/s390/kvm/kvm-s390.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >> index f329dcb3f44c..49d7722229ae 100644 >> --- a/arch/s390/kvm/kvm-s390.c >> +++ b/arch/s390/kvm/kvm-s390.c >> @@ -4255,7 +4255,7 @@ 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) > > Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx> >
