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 7CE696B0271 for ; Sat, 16 Dec 2017 14:30:10 -0500 (EST) Received: by mail-lf0-f71.google.com with SMTP id m3so2992091lfe.3 for ; Sat, 16 Dec 2017 11:30:10 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id x88sor377040lfi.105.2017.12.16.11.30.08 for (Google Transport Security); Sat, 16 Dec 2017 11:30:08 -0800 (PST) From: Aliaksei Karaliou Subject: [PATCH] mm: vmscan: make unregister_shrinker() safer Date: Sat, 16 Dec 2017 22:29:37 +0300 Message-Id: <20171216192937.13549-1-akaraliou.dev@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org, mhocko@suse.com, hannes@cmpxchg.org, hillf.zj@alibaba-inc.com, minchan@kernel.org Cc: Aliaksei Karaliou , linux-mm@kvack.org unregister_shrinker() does not have any sanitizing inside so calling it twice will oops because of double free attempt or so. This patch makes unregister_shrinker() safer and allows calling it on resource freeing path without explicit knowledge of whether shrinker was successfully registered or not. Signed-off-by: Aliaksei Karaliou --- mm/vmscan.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 65c4fa26abfa..7cb56db5e9ca 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -281,10 +281,14 @@ 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); -- 2.11.0 -- 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