From patchwork Fri Jun 12 19:15:51 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 11602233 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 54E536A2 for ; Fri, 12 Jun 2020 19:20:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3763E206D7 for ; Fri, 12 Jun 2020 19:20:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726343AbgFLTUZ (ORCPT ); Fri, 12 Jun 2020 15:20:25 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:57898 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726268AbgFLTUY (ORCPT ); Fri, 12 Jun 2020 15:20:24 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out02.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jjpDl-0004PN-Dk; Fri, 12 Jun 2020 13:20:09 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1jjpDd-0006RR-MZ; Fri, 12 Jun 2020 13:20:09 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: syzbot Cc: a@unstable.cc, adobriyan@gmail.com, akpm@linux-foundation.org, alex.dewar@gmx.co.uk, amir73il@gmail.com, anton.ivanov@cambridgegreys.com, b.a.t.m.a.n@lists.open-mesh.org, davem@davemloft.net, jack@suse.cz, jdike@addtoit.com, kuba@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-um@lists.infradead.org, mareklindner@neomailbox.ch, netdev@vger.kernel.org, richard@nod.at, sfr@canb.auug.org.au, sven@narfation.org, sw@simonwunderlich.de, syzkaller-bugs@googlegroups.com References: <000000000000d788c905a7dfa3f4@google.com> Date: Fri, 12 Jun 2020 14:15:51 -0500 In-Reply-To: <000000000000d788c905a7dfa3f4@google.com> (syzbot's message of "Fri, 12 Jun 2020 02:24:11 -0700") Message-ID: <87mu58p02g.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1jjpDd-0006RR-MZ;;;mid=<87mu58p02g.fsf@x220.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19vy/8HlHfqiCxlfZY83od+GSsaBZEU8Is= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on sa01.xmission.com X-Spam-Level: *** X-Spam-Status: No, score=3.5 required=8.0 tests=ALL_TRUSTED,BAYES_50, DCC_CHECK_NEGATIVE,LotsOfNums_01,NO_DNS_FOR_FROM,SORTED_RECIPS, T_TM2_M_HEADER_IN_MSG autolearn=disabled version=3.4.2 X-Spam-Virus: No X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.4825] * 2.5 SORTED_RECIPS Recipient list is sorted by address * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * 1.2 LotsOfNums_01 BODY: Lots of long strings of numbers * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa01 0; Body=1 Fuz1=1 Fuz2=1] * 0.0 NO_DNS_FOR_FROM DNS: Envelope sender has no MX or A DNS records X-Spam-DCC: ; sa01 0; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ***;syzbot X-Spam-Relay-Country: X-Spam-Timing: total 7251 ms - load_scoreonly_sql: 0.03 (0.0%), signal_user_changed: 3.9 (0.1%), b_tie_ro: 2.8 (0.0%), parse: 0.68 (0.0%), extract_message_metadata: 12 (0.2%), get_uri_detail_list: 1.77 (0.0%), tests_pri_-1000: 2.7 (0.0%), tests_pri_-950: 0.97 (0.0%), tests_pri_-900: 0.84 (0.0%), tests_pri_-90: 139 (1.9%), check_bayes: 138 (1.9%), b_tokenize: 8 (0.1%), b_tok_get_all: 8 (0.1%), b_comp_prob: 1.97 (0.0%), b_tok_touch_all: 117 (1.6%), b_finish: 0.72 (0.0%), tests_pri_0: 6340 (87.4%), check_dkim_signature: 0.39 (0.0%), check_dkim_adsp: 6008 (82.9%), poll_dns_idle: 6742 (93.0%), tests_pri_10: 2.6 (0.0%), tests_pri_500: 746 (10.3%), rewrite_mail: 0.00 (0.0%) Subject: [PATCH] proc: Use new_inode not new_inode_pseudo X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Recently syzbot reported that unmounting proc when there is an ongoing inotify watch on the root directory of proc could result in a use after free when the watch is removed after the unmount of proc when the watcher exits. Commit 69879c01a0c3 ("proc: Remove the now unnecessary internal mount of proc") made it easier to unmount proc and allowed syzbot to see the problem, but looking at the code it has been around for a long time. Looking at the code the fsnotify watch should have been removed by fsnotify_sb_delete in generic_shutdown_super. Unfortunately the inode was allocated with new_inode_pseudo instead of new_inode so the inode was not on the sb->s_inodes list. Which prevented fsnotify_unmount_inodes from finding the inode and removing the watch as well as made it so the "VFS: Busy inodes after unmount" warning could not find the inodes to warn about them. Make all of the inodes in proc visible to generic_shutdown_super, and fsnotify_sb_delete by using new_inode instead of new_inode_pseudo. The only functional difference is that new_inode places the inodes on the sb->s_inodes list. I wrote a small test program and I can verify that without changes it can trigger this issue, and by replacing new_inode_pseudo with new_inode the issues goes away. Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/000000000000d788c905a7dfa3f4@google.com Reported-by: syzbot+7d2debdcdb3cb93c1e5e@syzkaller.appspotmail.com Fixes: 0097875bd415 ("proc: Implement /proc/thread-self to point at the directory of the current thread") Fixes: 021ada7dff22 ("procfs: switch /proc/self away from proc_dir_entry") Fixes: 51f0885e5415 ("vfs,proc: guarantee unique inodes in /proc") Signed-off-by: "Eric W. Biederman" Reviewed-by: Jan Kara --- fs/proc/inode.c | 2 +- fs/proc/self.c | 2 +- fs/proc/thread_self.c | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/proc/inode.c b/fs/proc/inode.c index f40c2532c057..28d6105e908e 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -617,7 +617,7 @@ const struct inode_operations proc_link_inode_operations = { struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de) { - struct inode *inode = new_inode_pseudo(sb); + struct inode *inode = new_inode(sb); if (inode) { inode->i_ino = de->low_ino; diff --git a/fs/proc/self.c b/fs/proc/self.c index ca5158fa561c..72cd69bcaf4a 100644 --- a/fs/proc/self.c +++ b/fs/proc/self.c @@ -43,7 +43,7 @@ int proc_setup_self(struct super_block *s) inode_lock(root_inode); self = d_alloc_name(s->s_root, "self"); if (self) { - struct inode *inode = new_inode_pseudo(s); + struct inode *inode = new_inode(s); if (inode) { inode->i_ino = self_inum; inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode); diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c index ac284f409568..a553273fbd41 100644 --- a/fs/proc/thread_self.c +++ b/fs/proc/thread_self.c @@ -43,7 +43,7 @@ int proc_setup_thread_self(struct super_block *s) inode_lock(root_inode); thread_self = d_alloc_name(s->s_root, "thread-self"); if (thread_self) { - struct inode *inode = new_inode_pseudo(s); + struct inode *inode = new_inode(s); if (inode) { inode->i_ino = thread_self_inum; inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);