Re: [PATCH v2] mm/swapfile: unuse_pte can map random data if swap read fails

Peter Xu
2022-04-20T13:32:44Z

On Wed, Apr 20, 2022 at 02:21:27PM +0800, Miaohe Lin wrote:
> On 2022/4/20 5:36, Peter Xu wrote:
> > On Sat, Apr 16, 2022 at 11:05:49AM +0800, Miaohe Lin wrote:
> >> @@ -1797,6 +1797,17 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
> >> goto out;
> >> }
> >>
> >> + if (unlikely(!PageUptodate(page))) {
> >> + pte_t pteval;
> >> +
> >> + dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
> >> + pteval = swp_entry_to_pte(make_swapin_error_entry(page));
> >> + set_pte_at(vma->vm_mm, addr, pte, pteval);
> >> + swap_free(entry);
> >> + ret = 0;
> >> + goto out;
> >> + }
> >> +
> >> /* See do_swap_page() */
> >> BUG_ON(!PageAnon(page) && PageMappedToDisk(page));
> >> BUG_ON(PageAnon(page) && PageAnonExclusive(page));
> >
> > Totally off-topic, but.. today when I was looking at the unuse path I just
> > found that the swp bits could have got lost for either soft-dirty and
> > uffd-wp here? A quick patch attached.
>
> Am I supposed to test-and-send this patch? The patch looks good to me except the
> build error pointed out by kernel test robot.

I was planning to post a patch after yours since they're touching the same
function, but yeah it'll be great if you could also take that over, thanks!

--
Peter Xu