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[12/19] mm/migrate: fixup setting UFFD_WP flag

Message ID 20200904233558.ivUQZ2xpI%akpm@linux-foundation.org
State New
Headers show
Series [01/19] memcg: fix use-after-free in uncharge_batch | expand

Commit Message

Andrew Morton Sept. 4, 2020, 11:35 p.m. UTC
From: Alistair Popple <alistair@popple.id.au>
Subject: 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.

Link: https://lkml.kernel.org/r/20200825064232.10023-1-alistair@popple.id.au
Fixes: f45ec5ff16a75 ("userfaultfd: wp: support swap and page migration")
Signed-off-by: Alistair Popple <alistair@popple.id.au>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

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

--- a/mm/migrate.c~mm-migrate-fixup-setting-uffd_wp-flag
+++ a/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);
 			}
 		}