From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:57136 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161538AbeE1Kgh (ORCPT ); Mon, 28 May 2018 06:36:37 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Danilo Krummrich , Kees Cook , Andrew Morton , "Luis R . Rodriguez" , "Eric W. Biederman" , Alexey Dobriyan , Linus Torvalds , Sasha Levin Subject: [PATCH 4.9 232/329] fs/proc/proc_sysctl.c: fix potential page fault while unregistering sysctl table Date: Mon, 28 May 2018 12:02:41 +0200 Message-Id: <20180528100301.401236771@linuxfoundation.org> In-Reply-To: <20180528100241.796630982@linuxfoundation.org> References: <20180528100241.796630982@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Danilo Krummrich [ Upstream commit a0b0d1c345d0317efe594df268feb5ccc99f651e ] proc_sys_link_fill_cache() does not take currently unregistering sysctl tables into account, which might result into a page fault in sysctl_follow_link() - add a check to fix it. This bug has been present since v3.4. Link: http://lkml.kernel.org/r/20180228013506.4915-1-danilokrummrich@dk-develop.de Fixes: 0e47c99d7fe25 ("sysctl: Replace root_list with links between sysctl_table_sets") Signed-off-by: Danilo Krummrich Acked-by: Kees Cook Reviewed-by: Andrew Morton Cc: "Luis R . Rodriguez" Cc: "Eric W. Biederman" Cc: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/proc/proc_sysctl.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -660,7 +660,10 @@ static bool proc_sys_link_fill_cache(str struct ctl_table *table) { bool ret = true; + head = sysctl_head_grab(head); + if (IS_ERR(head)) + return false; if (S_ISLNK(table->mode)) { /* It is not an error if we can not follow the link ignore it */