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=0.1 required=3.0 tests=DATE_IN_PAST_12_24, FROM_LOCAL_HEX,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 6E71FC282DF for ; Fri, 19 Apr 2019 18:52:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3AF9E20663 for ; Fri, 19 Apr 2019 18:52:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728317AbfDSSwh (ORCPT ); Fri, 19 Apr 2019 14:52:37 -0400 Received: from mail-io1-f71.google.com ([209.85.166.71]:51630 "EHLO mail-io1-f71.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728075AbfDSSwg (ORCPT ); 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2002:a6b:f201:: with SMTP id q1mr1485570ioh.197.1555651504890; Thu, 18 Apr 2019 22:25:04 -0700 (PDT) Date: Thu, 18 Apr 2019 22:25:04 -0700 In-Reply-To: <00000000000044cbf80576baaecd@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <00000000000057eb510586db5717@google.com> Subject: Re: possible deadlock in path_openat From: syzbot To: amir73il@gmail.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-unionfs@vger.kernel.org, miklos@szeredi.hu, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org syzbot has found a reproducer for the following crash on: HEAD commit: 3f018f4a Add linux-next specific files for 20190418 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=128f767b200000 kernel config: https://syzkaller.appspot.com/x/.config?x=faa7bdc352fc157e dashboard link: https://syzkaller.appspot.com/bug?extid=a55ccfc8a853d3cff213 compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14fb9457200000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+a55ccfc8a853d3cff213@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected 5.1.0-rc5-next-20190418 #28 Not tainted ------------------------------------------------------ syz-executor.0/8098 is trying to acquire lock: 000000006bd07a6a (&ovl_i_mutex_dir_key[depth]#2){++++}, at: inode_lock_shared include/linux/fs.h:782 [inline] 000000006bd07a6a (&ovl_i_mutex_dir_key[depth]#2){++++}, at: do_last fs/namei.c:3321 [inline] 000000006bd07a6a (&ovl_i_mutex_dir_key[depth]#2){++++}, at: path_openat+0x1e98/0x46e0 fs/namei.c:3533 but task is already holding lock: 0000000046f9863b (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds fs/exec.c:1407 [inline] 0000000046f9863b (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x376/0x23f0 fs/exec.c:1750 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&sig->cred_guard_mutex){+.+.}: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1310 kernel/locking/mutex.c:1072 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1102 do_io_accounting+0x1f4/0x830 fs/proc/base.c:2739 proc_tgid_io_accounting+0x23/0x30 fs/proc/base.c:2788 proc_single_show+0xf6/0x170 fs/proc/base.c:743 seq_read+0x4db/0x1130 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:701 [inline] do_loop_readv_writev fs/read_write.c:688 [inline] do_iter_read+0x4a9/0x660 fs/read_write.c:922 vfs_readv+0xf0/0x160 fs/read_write.c:984 kernel_readv fs/splice.c:358 [inline] default_file_splice_read+0x475/0x890 fs/splice.c:413 do_splice_to+0x12a/0x190 fs/splice.c:876 do_splice+0x110b/0x1420 fs/splice.c:1183 __do_sys_splice fs/splice.c:1424 [inline] __se_sys_splice fs/splice.c:1404 [inline] __x64_sys_splice+0x2c6/0x330 fs/splice.c:1404 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #3 (&p->lock){+.+.}: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1310 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 seq_read+0x71/0x1130 fs/seq_file.c:161 proc_reg_read+0x1fe/0x2c0 fs/proc/inode.c:227 do_loop_readv_writev fs/read_write.c:701 [inline] do_loop_readv_writev fs/read_write.c:688 [inline] do_iter_read+0x4a9/0x660 fs/read_write.c:922 vfs_readv+0xf0/0x160 fs/read_write.c:984 kernel_readv fs/splice.c:358 [inline] default_file_splice_read+0x475/0x890 fs/splice.c:413 do_splice_to+0x12a/0x190 fs/splice.c:876 do_splice+0x110b/0x1420 fs/splice.c:1183 __do_sys_splice fs/splice.c:1424 [inline] __se_sys_splice fs/splice.c:1404 [inline] __x64_sys_splice+0x2c6/0x330 fs/splice.c:1404 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (&pipe->mutex/1){+.+.}: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1310 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 pipe_lock_nested fs/pipe.c:62 [inline] pipe_lock+0x6e/0x80 fs/pipe.c:70 iter_file_splice_write+0x18b/0xbe0 fs/splice.c:696 do_splice_from fs/splice.c:847 [inline] do_splice+0x70a/0x1420 fs/splice.c:1154 __do_sys_splice fs/splice.c:1424 [inline] __se_sys_splice fs/splice.c:1404 [inline] __x64_sys_splice+0x2c6/0x330 fs/splice.c:1404 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (sb_writers#5){.+.+}: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 percpu_down_read include/linux/percpu-rwsem.h:36 [inline] __sb_start_write+0x20b/0x360 fs/super.c:1613 sb_start_write include/linux/fs.h:1621 [inline] mnt_want_write+0x3f/0xc0 fs/namespace.c:358 ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:24 ovl_do_remove+0xe9/0xd70 fs/overlayfs/dir.c:840 ovl_rmdir+0x1b/0x20 fs/overlayfs/dir.c:890 vfs_rmdir fs/namei.c:3878 [inline] vfs_rmdir+0x19c/0x470 fs/namei.c:3857 do_rmdir+0x39e/0x420 fs/namei.c:3939 __do_sys_rmdir fs/namei.c:3957 [inline] __se_sys_rmdir fs/namei.c:3955 [inline] __x64_sys_rmdir+0x36/0x40 fs/namei.c:3955 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&ovl_i_mutex_dir_key[depth]#2){++++}: check_prevs_add kernel/locking/lockdep.c:2322 [inline] validate_chain kernel/locking/lockdep.c:2703 [inline] __lock_acquire+0x239c/0x3fb0 kernel/locking/lockdep.c:3690 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 down_read+0x3f/0x1a0 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:782 [inline] do_last fs/namei.c:3321 [inline] path_openat+0x1e98/0x46e0 fs/namei.c:3533 do_filp_open+0x1a1/0x280 fs/namei.c:3563 do_open_execat+0x137/0x690 fs/exec.c:856 __do_execve_file.isra.0+0x178d/0x23f0 fs/exec.c:1758 do_execveat_common fs/exec.c:1865 [inline] do_execve fs/exec.c:1882 [inline] __do_sys_execve fs/exec.c:1958 [inline] __se_sys_execve fs/exec.c:1953 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1953 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &ovl_i_mutex_dir_key[depth]#2 --> &p->lock --> &sig->cred_guard_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sig->cred_guard_mutex); lock(&p->lock); lock(&sig->cred_guard_mutex); lock(&ovl_i_mutex_dir_key[depth]#2); *** DEADLOCK *** 1 lock held by syz-executor.0/8098: #0: 0000000046f9863b (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds fs/exec.c:1407 [inline] #0: 0000000046f9863b (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x376/0x23f0 fs/exec.c:1750 stack backtrace: CPU: 0 PID: 8098 Comm: syz-executor.0 Not tainted 5.1.0-rc5-next-20190418 #28 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x172/0x1f0 lib/dump_stack.c:113 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1560 check_prev_add.constprop.0+0xf11/0x23c0 kernel/locking/lockdep.c:2209 check_prevs_add kernel/locking/lockdep.c:2322 [inline] validate_chain kernel/locking/lockdep.c:2703 [inline] __lock_acquire+0x239c/0x3fb0 kernel/locking/lockdep.c:3690 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 down_read+0x3f/0x1a0 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:782 [inline] do_last fs/namei.c:3321 [inline] path_openat+0x1e98/0x46e0 fs/namei.c:3533 do_filp_open+0x1a1/0x280 fs/namei.c:3563 do_open_execat+0x137/0x690 fs/exec.c:856 __do_execve_file.isra.0+0x178d/0x23f0 fs/exec.c:1758 do_execveat_common fs/exec.c:1865 [inline] do_execve fs/exec.c:1882 [inline] __do_sys_execve fs/exec.c:1958 [inline] __se_sys_execve fs/exec.c:1953 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1953 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x458c29 Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f5db8befc78 EFLAGS: 00000246 ORIG_RAX: 000000000000003b RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458c29 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000000 RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f5db8bf06d4 R13: 00000000004bf216 R14: 00000000004d0458 R15: 00000000ffffffff