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

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Message-ID: <YmALdt9MV2MI9FRp@xz-m1.local>
Date:   Wed, 20 Apr 2022 09:32:38 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     akpm@...ux-foundation.org, willy@...radead.org, vbabka@...e.cz,
        dhowells@...hat.com, neilb@...e.de, david@...hat.com,
        apopple@...dia.com, surenb@...gle.com, minchan@...nel.org,
        sfr@...b.auug.org.au, rcampbell@...dia.com,
        naoya.horiguchi@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/swapfile: unuse_pte can map random data if swap
 read fails

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