linux-kernel - Re: [PATCH 1/2] mm/migrate: Fixup setting UFFD

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Message-ID: <20200824154452.GB8605@xz-x1>
Date:   Mon, 24 Aug 2020 11:44:52 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Alistair Popple <alistair@...ple.id.au>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] mm/migrate: Fixup setting UFFD_WP flag

On Mon, Aug 24, 2020 at 06:31:27PM +1000, Alistair Popple wrote:
> Commit f45ec5ff16a75 ("userfaultfd: wp: support swap and page
> migration") introduced support for tracking the uffd wp bit during page
> migration. However the non-swap PTE variant was used to set the flag for
> zone device private pages which are a type of swap page.
> 
> This leads to corruption of the swap offset if the original PTE has the
> uffd_wp flag set.
> 
> Fixes: f45ec5ff16a75 ("userfaultfd: wp: support swap and page migration")
> Signed-off-by: Alistair Popple <alistair@...ple.id.au>
> Cc: stable@...r.kernel.org
> ---
>  mm/migrate.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 34a842a8eb6a..ddb64253fe3e 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -251,7 +251,7 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
>  				entry = make_device_private_entry(new, pte_write(pte));
>  				pte = swp_entry_to_pte(entry);
>  				if (pte_swp_uffd_wp(*pvmw.pte))
> -					pte = pte_mkuffd_wp(pte);
> +					pte = pte_swp_mkuffd_wp(pte);
>  			}
>  		}

Looks correct... thanks!

Reviewed-by: Peter Xu <peterx@...hat.com>

-- 
Peter Xu