From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752812AbbGKGml (ORCPT ); Sat, 11 Jul 2015 02:42:41 -0400 Received: from mail-pd0-f178.google.com ([209.85.192.178]:34429 "EHLO mail-pd0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751602AbbGKGmk (ORCPT ); Sat, 11 Jul 2015 02:42:40 -0400 From: Sergey Senozhatsky To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [PATCH 1/2] mm/shrinker: do not NULL dereference uninitialized shrinker Date: Sat, 11 Jul 2015 11:51:54 +0900 Message-Id: <1436583115-6323-2-git-send-email-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.4.5 In-Reply-To: <1436583115-6323-1-git-send-email-sergey.senozhatsky@gmail.com> References: <1436583115-6323-1-git-send-email-sergey.senozhatsky@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Consider 'all zeroes' shrinker as 'initialized, but not registered', and, thus, don't unregister such a shrinker. This helps to avoid accidental NULL pointer dereferences, when a zeroed shrinker struct is getting passed to unregister_shrinker() in error handing path, for example. Signed-off-by: Sergey Senozhatsky --- mm/vmscan.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index c8d8282..cadc8a2 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -254,6 +254,12 @@ EXPORT_SYMBOL(register_shrinker); */ void unregister_shrinker(struct shrinker *shrinker) { + /* + * All-zeroes is 'initialized, but not registered' shrinker. + */ + if (unlikely(!shrinker->list.next)) + return; + down_write(&shrinker_rwsem); list_del(&shrinker->list); up_write(&shrinker_rwsem); -- 2.4.5