[PATCH 3.2 075/102] mm: migrate: Close race between migration completion and mprotect
3.2.64-rc1 review patch. If anyone has any objections, please let me know. -- From: Mel Gorman 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. [torva...@linux-foundation.org: use maybe_mkwrite] Signed-off-by: Mel Gorman Acked-by: Rik van Riel Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- mm/migrate.c | 5 - 1 file changed, 4 insertions(+), 1 deletion(-) --- a/mm/migrate.c +++ b/mm/migrate.c @@ -141,8 +141,11 @@ static int remove_migration_pte(struct p get_page(new); pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); + + /* 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 3.2 075/102] mm: migrate: Close race between migration completion and mprotect
3.2.64-rc1 review patch. If anyone has any objections, please let me know. -- From: Mel Gorman mgor...@suse.de 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. [torva...@linux-foundation.org: use maybe_mkwrite] Signed-off-by: Mel Gorman mgor...@suse.de Acked-by: Rik van Riel r...@redhat.com Signed-off-by: Linus Torvalds torva...@linux-foundation.org [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings b...@decadent.org.uk --- mm/migrate.c | 5 - 1 file changed, 4 insertions(+), 1 deletion(-) --- a/mm/migrate.c +++ b/mm/migrate.c @@ -141,8 +141,11 @@ static int remove_migration_pte(struct p get_page(new); pte = pte_mkold(mk_pte(new, vma-vm_page_prot)); + + /* 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); -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
