diff options
| author | Mel Gorman <mgorman@suse.de> | 2014-10-02 19:47:41 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-10-09 12:21:26 -0700 |
| commit | 5b81f9368aa61e521599a23d576c01bc655f95e7 (patch) | |
| tree | 713be7d37ec3ffbc4787e4735f5db5d8230e7118 | |
| parent | fddac5ed7699cbf4828f7493d4995e739d6fe6a5 (diff) | |
| download | lwn-5b81f9368aa61e521599a23d576c01bc655f95e7.tar.gz lwn-5b81f9368aa61e521599a23d576c01bc655f95e7.zip | |
mm: migrate: Close race between migration completion and mprotect
commit d3cb8bf6081b8b7a2dabb1264fe968fd870fa595 upstream.
A migration entry is marked as write if pte_write was true at the time the
entry was created. The VMA protections are not double checked when migration
entries are being removed as mprotect marks write-migration-entries as
read. It means that potentially we take a spurious fault to mark PTEs write
again but it's straight-forward. However, there is a race between write
migrations being marked read and migrations finishing. This potentially
allows a PTE to be write that should have been read. Close this race by
double checking the VMA permissions using maybe_mkwrite when migration
completes.
[torvalds@linux-foundation.org: use maybe_mkwrite]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | mm/migrate.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index bed48809e5d0..13f47fbe3550 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -148,8 +148,11 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma, pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); if (pte_swp_soft_dirty(*ptep)) pte = pte_mksoft_dirty(pte); + + /* Recheck VMA as permissions can change since migration started */ if (is_write_migration_entry(entry)) - pte = pte_mkwrite(pte); + pte = maybe_mkwrite(pte, vma); + #ifdef CONFIG_HUGETLB_PAGE if (PageHuge(new)) { pte = pte_mkhuge(pte); |