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

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Message-ID: <8d180899-9ae2-a38b-3642-ffd057b7acaf@huawei.com>
Date:   Thu, 21 Apr 2022 09:50:06 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Peter Xu <peterx@...hat.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 2022/4/20 21:32, Peter Xu wrote:
> 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!

Sure, I will take this in next version. Thanks a lot! :)

>