linux-kernel - [PATCH 5.8 181/186] mm/migrate: fixup setting UFFD

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Date:   Tue,  8 Sep 2020 17:25:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alistair Popple <alistair@...ple.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Xu <peterx@...hat.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.8 181/186] mm/migrate: fixup setting UFFD_WP flag

From: Alistair Popple <alistair@...ple.id.au>

commit ebdf8321eeeb623aed60f7ed16f7445363230118 upstream.

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>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Peter Xu <peterx@...hat.com>
Cc: Jérôme Glisse <jglisse@...hat.com>
Cc: John Hubbard <jhubbard@...dia.com>
Cc: Ralph Campbell <rcampbell@...dia.com>
Link: https://lkml.kernel.org/r/20200825064232.10023-1-alistair@popple.id.au
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/migrate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -251,7 +251,7 @@ static bool remove_migration_pte(struct
 				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);
 			}
 		}