From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f71.google.com (mail-lf0-f71.google.com [209.85.215.71]) by kanga.kvack.org (Postfix) with ESMTP id 747C66B0038 for ; Wed, 13 Sep 2017 10:29:41 -0400 (EDT) Received: by mail-lf0-f71.google.com with SMTP id q132so297622lfe.1 for ; Wed, 13 Sep 2017 07:29:41 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id n190sor3085815lfb.110.2017.09.13.07.29.39 for (Google Transport Security); Wed, 13 Sep 2017 07:29:39 -0700 (PDT) Date: Wed, 13 Sep 2017 16:29:37 +0200 From: Vitaly Wool Subject: z3fold: fix potential race in z3fold_reclaim_page Message-Id: <20170913162937.bfff21c7d12b12a5f47639fd@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Linux-MM , linux-kernel@vger.kernel.org Cc: Dan Streetman , Andrew Morton , Oleksiy.Avramchenko@sony.com It is possible that on a (partially) unsuccessful page reclaim, kref_put() called in z3fold_reclaim_page() does not yield page release, but the page is released shortly afterwards by another thread. Then z3fold_reclaim_page() would try to list_add() that (released) page again which is obviously a bug. To avoid that, spin_lock() has to be taken earlier, before the kref_put() call mentioned earlier. Signed-off-by: Vitaly Wool --- mm/z3fold.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/z3fold.c b/mm/z3fold.c index 486550df32be..b04fa3ba1bf2 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -875,16 +875,18 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) goto next; } next: + spin_lock(&pool->lock); if (test_bit(PAGE_HEADLESS, &page->private)) { if (ret == 0) { + spin_unlock(&pool->lock); free_z3fold_page(page); return 0; } } else if (kref_put(&zhdr->refcount, release_z3fold_page)) { atomic64_dec(&pool->pages_nr); + spin_unlock(&pool->lock); return 0; } - spin_lock(&pool->lock); /* * Add to the beginning of LRU. -- 2.11.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org