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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 156AAC433DF for ; Fri, 15 May 2020 15:37:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 01BE4207C4 for ; Fri, 15 May 2020 15:37:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726584AbgEOPhN (ORCPT ); Fri, 15 May 2020 11:37:13 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:56988 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726183AbgEOPhM (ORCPT ); Fri, 15 May 2020 11:37:12 -0400 Received: from fsav405.sakura.ne.jp (fsav405.sakura.ne.jp [133.242.250.104]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 04FFaX5p011041; Sat, 16 May 2020 00:36:33 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav405.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav405.sakura.ne.jp); Sat, 16 May 2020 00:36:33 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav405.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 04FFaXJU011017 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sat, 16 May 2020 00:36:33 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: linux-next boot error: general protection fault in tomoyo_get_local_path From: Tetsuo Handa To: Alexey Gladkov , "Eric W. Biederman" , Alexander Viro Cc: syzbot , jmorris@namei.org, linux-kernel@vger.kernel.org, linux-next@vger.kernel.org, linux-security-module@vger.kernel.org, serge@hallyn.com, sfr@canb.auug.org.au, syzkaller-bugs@googlegroups.com, linux-fsdevel References: <0000000000002f0c7505a5b0e04c@google.com> Message-ID: <72cb7aea-92bd-d71b-2f8a-63881a35fad8@i-love.sakura.ne.jp> Date: Sat, 16 May 2020 00:36:28 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-next-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-next@vger.kernel.org On 2020/05/16 0:18, Tetsuo Handa wrote: > This is > > if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') { > char *ep; > const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10); > struct pid_namespace *proc_pidns = proc_pid_ns(d_inode(dentry)); // <= here > > if (*ep == '/' && pid && pid == > task_tgid_nr_ns(current, proc_pidns)) { > > which was added by commit c59f415a7cb6e1e1 ("Use proc_pid_ns() to get pid_namespace from the proc superblock"). > > @@ -161,9 +162,10 @@ static char *tomoyo_get_local_path(struct dentry *dentry, char * const buffer, > if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') { > char *ep; > const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10); > + struct pid_namespace *proc_pidns = proc_pid_ns(d_inode(dentry)); > > if (*ep == '/' && pid && pid == > - task_tgid_nr_ns(current, sb->s_fs_info)) { > + task_tgid_nr_ns(current, proc_pidns)) { > pos = ep - 5; > if (pos < buffer) > goto out; > > Alexey and Eric, any clue? > A similar bug (racing inode destruction with open() on proc filesystem) was fixed as commit 6f7c41374b62fd80 ("tomoyo: Don't use nifty names on sockets."). Then, it might not be safe to replace dentry->d_sb->s_fs_info with dentry->d_inode->i_sb->s_fs_info .