From b997052bc3ac444a0bceab1093aff7ae71ed419e Mon Sep 17 00:00:00 2001 From: Henry Burns Date: Tue, 13 Aug 2019 15:37:25 -0700 Subject: mm/z3fold.c: fix z3fold_destroy_pool() race condition The constraint from the zpool use of z3fold_destroy_pool() is there are no outstanding handles to memory (so no active allocations), but it is possible for there to be outstanding work on either of the two wqs in the pool. Calling z3fold_deregister_migration() before the workqueues are drained means that there can be allocated pages referencing a freed inode, causing any thread in compaction to be able to trip over the bad pointer in PageMovable(). Link: http://lkml.kernel.org/r/20190726224810.79660-2-henryburns@google.com Fixes: 1f862989b04a ("mm/z3fold.c: support page migration") Signed-off-by: Henry Burns Reviewed-by: Shakeel Butt Reviewed-by: Jonathan Adams Cc: Vitaly Vul Cc: Vitaly Wool Cc: David Howells Cc: Thomas Gleixner Cc: Al Viro Cc: Henry Burns Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/z3fold.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'mm') diff --git a/mm/z3fold.c b/mm/z3fold.c index 43de92f52961..ed19d98c9dcd 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -817,16 +817,19 @@ out: static void z3fold_destroy_pool(struct z3fold_pool *pool) { kmem_cache_destroy(pool->c_handle); - z3fold_unregister_migration(pool); /* * We need to destroy pool->compact_wq before pool->release_wq, * as any pending work on pool->compact_wq will call * queue_work(pool->release_wq, &pool->work). + * + * There are still outstanding pages until both workqueues are drained, + * so we cannot unregister migration until then. */ destroy_workqueue(pool->compact_wq); destroy_workqueue(pool->release_wq); + z3fold_unregister_migration(pool); kfree(pool); } -- cgit v1.2.3-59-g8ed1b