On Mon, 2023-12-11 at 11:26 +0100, Alexander Potapenko wrote:
> > +static inline void *arch_kmsan_get_meta_or_null(void *addr, bool
> > is_origin)
> > +{
> > + if (addr >= (void *)&S390_lowcore &&
> > + addr < (void *)(&S390_lowcore + 1)) {
> > + /*
> > + * Different lowcores accessed via S390_lowcore are
> > described
> > + * by the same struct page. Resolve the prefix
> > manually in
> > + * order to get a distinct struct page.
> > + */
> > + addr += (void *)lowcore_ptr[raw_smp_processor_id()]
> > -
> > + (void *)&S390_lowcore;
> > + return kmsan_get_metadata(addr, is_origin);
> > + }
> > + return NULL;
> > +}
>
> Is there a possibility for infinite recursion here? E.g. can
> `lowcore_ptr[raw_smp_processor_id()]` point somewhere in between
> `(void *)&S390_lowcore` and `(void *)(&S390_lowcore + 1))`?
No, it's allocated with __get_free_pages() or memblock_alloc_low().
But since this question came up, I should probably add a check and
a WARN_ON_ONCE() here.
