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

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Message-Id: <20200824083128.12684-1-alistair@popple.id.au>
Date:   Mon, 24 Aug 2020 18:31:27 +1000
From:   Alistair Popple <alistair@...ple.id.au>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org,
        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>,
        Alistair Popple <alistair@...ple.id.au>, stable@...r.kernel.org
Subject: [PATCH 1/2] mm/migrate: Fixup setting UFFD_WP flag

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);
 			}
 		}
 
-- 
2.20.1