On Mon, Oct 05, 2020 at 12:11:39PM +0100, Matthew Wilcox wrote:
> On Mon, Oct 05, 2020 at 06:17:59AM +0300, Jarkko Sakkinen wrote:
> > @@ -317,10 +318,31 @@ int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start,
> > if (current->personality & READ_IMPLIES_EXEC)
> > return -EACCES;
> >
> > - xas_for_each(&xas, page, idx_end)
> > + /*
> > + * No need to hold encl->lock:
> > + * 1. None of the page->* get written.
> > + * 2. page->vm_max_prot_bits is set in sgx_encl_page_alloc(). This
> > + * is before calling xa_insert(). After that it is never modified.
> > + */
> > + xas_lock(&xas);
> > + xas_for_each(&xas, page, idx_end) {
> > + if (++count % XA_CHECK_SCHED)
> > + continue;
>
> This really doesn't do what you think it does.
>
> int ret = 0;
> int count = 0;
>
> xas_lock(&xas);
> while (xas.index < idx_end) {
> struct sgx_page *page = xas_next(&xas);
>
> if (!page || (~page->vm_max_prot_bits & vm_prot_bits)) {
> ret = -EACCESS;
> break;
> }
>
> if (++count % XA_CHECK_SCHED)
> continue;
> xas_pause(&xas);
> xas_unlock(&xas);
> cond_resched();
> xas_lock(&xas);
> }
> xas_unlock(&xas);
>
> return ret;
No mine certainly does not, it locks up the system if the loop succeeds
(i.e. does not return -EACCESS) :-) Unfortunately had by mistake the v1
patch (xa_load()) in the kernel that I used to test.
/Jarkko
