On Tue, Sep 10, 2024 at 12:54:19PM -0700, Dave Hansen wrote:
> On 9/6/24 04:49, Alexey Gladkov wrote:
> > +static inline bool is_kernel_addr(unsigned long addr)
> > +{
> > + return (long)addr < 0;
> > +}
> > +
> > static int handle_mmio(struct pt_regs *regs, struct ve_info *ve)
> > {
> > unsigned long *reg, val, vaddr;
> > @@ -434,6 +439,11 @@ static int handle_mmio(struct pt_regs *regs, struct ve_info *ve)
> > return -EINVAL;
> > }
> >
> > + if (!user_mode(regs) && !is_kernel_addr(ve->gla)) {
> > + WARN_ONCE(1, "Access to userspace address is not supported");
> > + return -EINVAL;
> > + }
>
> Should we really be open-coding a "is_kernel_addr" check? I mean,
> TASK_SIZE_MAX is there for a reason. While I doubt we'd ever change the
> positive vs. negative address space convention on 64-bit, I don't see a
> good reason to write a 64-bit x86-specific is_kernel_addr() when a more
> generic, portable and conventional idiom would do.
I took arch/x86/events/perf_event.h:1262 as an example. There is no
special reason in its own function.
> So, please use either a:
>
> addr < TASK_SIZE_MAX
>
> check, or use fault_in_kernel_space() directly.
I'll use fault_in_kernel_space() since SEV uses it. Thanks.
--
Rgrds, legion
