Re: [PATCH] KVM: SVM: Fix sparse: incorrect type in argument 1 (different base types)

[Brijesh Singh]

On 02/23/2018 12:05 PM, Paolo Bonzini wrote:
> On 22/02/2018 16:56, Brijesh Singh wrote:
> > On 02/21/2018 02:18 PM, Al Viro wrote:
> > > On Wed, Feb 21, 2018 at 01:59:55PM -0600, Brijesh Singh wrote:
> > >
> > > > Sure, checking access_ok() does not guarantee that later
> > > > copy_from_user() will not fail. But it does eliminate one possible
> > > > reason for the failure. We are trying to validate most of the user
> > > > inputs before we invoke SEV command.
> > >
> > > That makes no sense whatsoever. If user is deliberately fuzzing
> > > your code or trying to DoS it, that "validation" doesn't buy you
> > > anything - they can just as well feed you NULL, after all.
> >
> >
> > Currently, we let user query the blob length with params.len == 0 ||
> > param.uaddr == NULL. We could limit it to just params.len == 0.
> >
> >
> > > What is the rationale for that? "Userland is accidentally feeding
> > > us garbage pointers" is the case where slowness is the least of your
> > > concerns...
> >
> > My intent was to do some obvious failure checks on user inputs before
> > invoking the HW. I do see your point that if userspace is feeding us
> > garbage then slowness is least of our concern. If you think that we
> > should not be using access_ok() in this particular case then I am okay
> > with it.
>
> Can you please send a patch?  Thanks!

Sure, I will send patch soon.

-Brijesh