From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967385AbdLSN3F (ORCPT ); Tue, 19 Dec 2017 08:29:05 -0500 Received: from mail-pl0-f67.google.com ([209.85.160.67]:42964 "EHLO mail-pl0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936971AbdLSN26 (ORCPT ); Tue, 19 Dec 2017 08:28:58 -0500 X-Google-Smtp-Source: ACJfBouhslHXXVqulM5lQlEhhM0wIlKXIiGudWcMGs4nzjDHd4hNvStBP7qV7/+bRmPH4lVk9cn/eA== From: Michal Hocko To: Andrew Morton Cc: Al Viro , Tetsuo Handa , Aliaksei Karaliou , , , LKML , Glauber Costa , Michal Hocko Subject: [PATCH 1/2] mm,vmscan: Make unregister_shrinker() no-op if register_shrinker() failed. Date: Tue, 19 Dec 2017 14:28:43 +0100 Message-Id: <20171219132844.28354-2-mhocko@kernel.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20171219132844.28354-1-mhocko@kernel.org> References: <20171219132844.28354-1-mhocko@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tetsuo Handa Since allowing register_shrinker() callers to call unregister_shrinker() when register_shrinker() failed can simplify error recovery path, this patch makes unregister_shrinker() no-op when register_shrinker() failed. Let's also make sure that double unregister_shrinker doesn't blow up as well and NULL nr_deferred on successful de-registration to make the clean up even simpler and prevent from potential memory corruptions. [akaraliou.dev@gmail.com: set nr_deferred = NULL to handle double unregister] Signed-off-by: Tetsuo Handa Reported-by: syzbot Cc: Glauber Costa Cc: Al Viro Signed-off-by: Michal Hocko --- mm/vmscan.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 80dea50f421b..7a5801040fd4 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -281,10 +281,13 @@ EXPORT_SYMBOL(register_shrinker); */ void unregister_shrinker(struct shrinker *shrinker) { + if (!shrinker->nr_deferred) + return; down_write(&shrinker_rwsem); list_del(&shrinker->list); up_write(&shrinker_rwsem); kfree(shrinker->nr_deferred); + shrinker->nr_deferred = NULL; } EXPORT_SYMBOL(unregister_shrinker); -- 2.15.1