From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.5 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BFA7FC433DF for ; Wed, 10 Jun 2020 13:05:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9AD68206F4 for ; Wed, 10 Jun 2020 13:05:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729136AbgFJNFz (ORCPT ); Wed, 10 Jun 2020 09:05:55 -0400 Received: from raptor.unsafe.ru ([5.9.43.93]:53706 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729049AbgFJNFz (ORCPT ); Wed, 10 Jun 2020 09:05:55 -0400 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-89-102-33-211.net.upcbroadband.cz [89.102.33.211]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by raptor.unsafe.ru (Postfix) with ESMTPSA id F13D6203BD; Wed, 10 Jun 2020 13:05:52 +0000 (UTC) From: Alexey Gladkov To: ebiederm@xmission.com Cc: syzbot , adobriyan@gmail.com, keescook@chromium.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Subject: [PATCH] proc: s_fs_info may be NULL when proc_kill_sb is called Date: Wed, 10 Jun 2020 15:04:22 +0200 Message-Id: <20200610130422.1197386-1-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.4 In-Reply-To: <0000000000002d7ca605a7b8b1c5@google.com> References: <0000000000002d7ca605a7b8b1c5@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Wed, 10 Jun 2020 13:05:53 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org syzbot found that proc_fill_super() fails before filling up sb->s_fs_info, deactivate_locked_super() will be called and sb->s_fs_info will be NULL. The proc_kill_sb() does not expect fs_info to be NULL which is wrong. Link: https://lore.kernel.org/lkml/0000000000002d7ca605a7b8b1c5@google.com Reported-by: syzbot+4abac52934a48af5ff19@syzkaller.appspotmail.com Fixes: fa10fed30f25 ("proc: allow to mount many instances of proc in one pid namespace") Signed-off-by: Alexey Gladkov --- fs/proc/root.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/fs/proc/root.c b/fs/proc/root.c index ffebed1999e5..a715eb9f196a 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -264,15 +264,18 @@ static void proc_kill_sb(struct super_block *sb) { struct proc_fs_info *fs_info = proc_sb_info(sb); - if (fs_info->proc_self) - dput(fs_info->proc_self); + if (fs_info) { + if (fs_info->proc_self) + dput(fs_info->proc_self); - if (fs_info->proc_thread_self) - dput(fs_info->proc_thread_self); + if (fs_info->proc_thread_self) + dput(fs_info->proc_thread_self); + + put_pid_ns(fs_info->pid_ns); + kfree(fs_info); + } kill_anon_super(sb); - put_pid_ns(fs_info->pid_ns); - kfree(fs_info); } static struct file_system_type proc_fs_type = { -- 2.25.4