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=-5.4 required=3.0 tests=FROM_LOCAL_HEX, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 1B9A0C33C9E for ; Tue, 14 Jan 2020 22:04:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E1F1E24673 for ; Tue, 14 Jan 2020 22:04:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728901AbgANWEQ (ORCPT ); Tue, 14 Jan 2020 17:04:16 -0500 Received: from mail-il1-f199.google.com ([209.85.166.199]:48445 "EHLO mail-il1-f199.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728760AbgANWEO (ORCPT ); Tue, 14 Jan 2020 17:04:14 -0500 Received: by mail-il1-f199.google.com with SMTP id u14so11681483ilq.15 for ; Tue, 14 Jan 2020 14:04:13 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:date:message-id:subject:from:to; bh=3S9j3uq36gpvrhnH3ydXwg7I0WRc5NPGZffM/xDaOQ4=; b=HxQC+92dUVS8CnhYua3ozA+g2tGsEB6EhV2vX4HTd2N25RcKaVFTcwaJ5xo9Iu2Uoi n2PULSkQpcrLJh++55h8Oc7dhlyuC02iMcC7/3XzGgQ7zgFddcTjYJGwp2iGjw21suOc Uk8R0hAi1+PWO3ddxK4aGnTq+egdec/8Hwo/wn/wyJjwynVJSXgBMu+GasI6ODYSnAaN FKCqXXf+SLnrg/dAfhsPIhuUUXz/fxpr1H2l2zw+3l08no5YqWFuVmcJj1hdBtPbOeYP fo4QZiPnBt2GiD0zfu4oMeXktzj0U1dbejP873dsyRxO7Pa1WrSw8scdvutc1Sf2IUsD TDMA== X-Gm-Message-State: APjAAAUGxACntrzG3bMONh/1BT3ifoitQBXHH6hNBoL6tGj9htpAxBUd w/RUzeNo4FM0UhnBLt1n82/hZuZh0m4ogmwqURFsptYml6fP X-Google-Smtp-Source: APXvYqzGw7+E4Qb4MFTi8sqavJrANCW76Yc3mrQOOUjOJMiwlkeR/2ZHwvrF7c5DaAm/QvZ3i/RyhWMP5QoadwAoM6b53ReBqQpX MIME-Version: 1.0 X-Received: by 2002:a92:d18a:: with SMTP id z10mr663613ilz.48.1579039453602; Tue, 14 Jan 2020 14:04:13 -0800 (PST) Date: Tue, 14 Jan 2020 14:04:13 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <000000000000b7f160059c20c5a9@google.com> Subject: possible deadlock in proc_pid_stack From: syzbot To: adobriyan@gmail.com, akpm@linux-foundation.org, christian@brauner.io, guro@fb.com, kent.overstreet@gmail.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, mhocko@suse.com, syzkaller-bugs@googlegroups.com, tglx@linutronix.de 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 Hello, syzbot found the following crash on: HEAD commit: e033e7d4 Merge branch 'dhowells' (patches from DavidH) git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1499533ee00000 kernel config: https://syzkaller.appspot.com/x/.config?x=cfbb8fa33f49f9f3 dashboard link: https://syzkaller.appspot.com/bug?extid=c84a45dcab486e41c053 compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) Unfortunately, I don't have any reproducer for this crash yet. IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+c84a45dcab486e41c053@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected 5.5.0-rc6-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.5/21564 is trying to acquire lock: ffff8880a29cdf10 (&sig->cred_guard_mutex){+.+.}, at: lock_trace fs/proc/base.c:406 [inline] ffff8880a29cdf10 (&sig->cred_guard_mutex){+.+.}, at: proc_pid_stack+0xd9/0x200 fs/proc/base.c:450 but task is already holding lock: ffff8880a8bb30a0 (&p->lock){+.+.}, at: seq_read+0x6b/0xdb0 fs/seq_file.c:161 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&p->lock){+.+.}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4485 __mutex_lock_common+0x16e/0x2f30 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_nested+0x1b/0x30 kernel/locking/mutex.c:1118 seq_read+0x6b/0xdb0 fs/seq_file.c:161 proc_reg_read+0x1d5/0x2e0 fs/proc/inode.c:223 do_loop_readv_writev fs/read_write.c:714 [inline] do_iter_read+0x4a2/0x5b0 fs/read_write.c:935 vfs_readv+0xc2/0x120 fs/read_write.c:997 kernel_readv fs/splice.c:365 [inline] default_file_splice_read+0x579/0xa40 fs/splice.c:422 do_splice_to fs/splice.c:892 [inline] splice_direct_to_actor+0x3c9/0xb90 fs/splice.c:971 do_splice_direct+0x200/0x330 fs/splice.c:1080 do_sendfile+0x7e4/0xfd0 fs/read_write.c:1464 __do_sys_sendfile64 fs/read_write.c:1525 [inline] __se_sys_sendfile64 fs/read_write.c:1511 [inline] __x64_sys_sendfile64+0x176/0x1b0 fs/read_write.c:1511 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (sb_writers#3){.+.+}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4485 percpu_down_read include/linux/percpu-rwsem.h:40 [inline] __sb_start_write+0x189/0x420 fs/super.c:1674 sb_start_write include/linux/fs.h:1650 [inline] mnt_want_write+0x4a/0xa0 fs/namespace.c:354 ovl_want_write+0x77/0x80 fs/overlayfs/util.c:21 ovl_create_object+0xaf/0x2d0 fs/overlayfs/dir.c:596 ovl_create+0x29/0x30 fs/overlayfs/dir.c:627 lookup_open fs/namei.c:3241 [inline] do_last fs/namei.c:3331 [inline] path_openat+0x234d/0x4250 fs/namei.c:3537 do_filp_open+0x192/0x3d0 fs/namei.c:3567 do_sys_open+0x29f/0x560 fs/open.c:1097 ksys_open include/linux/syscalls.h:1383 [inline] __do_sys_creat fs/open.c:1155 [inline] __se_sys_creat fs/open.c:1153 [inline] __x64_sys_creat+0x65/0x70 fs/open.c:1153 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&ovl_i_mutex_dir_key[depth]#2){++++}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4485 down_read+0x39/0x50 kernel/locking/rwsem.c:1495 inode_lock_shared include/linux/fs.h:801 [inline] do_last fs/namei.c:3330 [inline] path_openat+0xa7a/0x4250 fs/namei.c:3537 do_filp_open+0x192/0x3d0 fs/namei.c:3567 do_open_execat+0xff/0x620 fs/exec.c:856 __do_execve_file+0x758/0x1cc0 fs/exec.c:1761 do_execveat_common fs/exec.c:1867 [inline] do_execve fs/exec.c:1884 [inline] __do_sys_execve fs/exec.c:1960 [inline] __se_sys_execve fs/exec.c:1955 [inline] __x64_sys_execve+0x94/0xb0 fs/exec.c:1955 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&sig->cred_guard_mutex){+.+.}: check_prev_add kernel/locking/lockdep.c:2476 [inline] check_prevs_add kernel/locking/lockdep.c:2581 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2971 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3955 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4485 __mutex_lock_common+0x16e/0x2f30 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_killable_nested+0x1b/0x30 kernel/locking/mutex.c:1133 lock_trace fs/proc/base.c:406 [inline] proc_pid_stack+0xd9/0x200 fs/proc/base.c:450 proc_single_show+0xe7/0x180 fs/proc/base.c:756 seq_read+0x4d8/0xdb0 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:714 [inline] do_iter_read+0x4a2/0x5b0 fs/read_write.c:935 vfs_readv fs/read_write.c:997 [inline] do_preadv+0x178/0x290 fs/read_write.c:1089 __do_sys_preadv fs/read_write.c:1139 [inline] __se_sys_preadv fs/read_write.c:1134 [inline] __x64_sys_preadv+0x9e/0xb0 fs/read_write.c:1134 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &sig->cred_guard_mutex --> sb_writers#3 --> &p->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&p->lock); lock(sb_writers#3); lock(&p->lock); lock(&sig->cred_guard_mutex); *** DEADLOCK *** 1 lock held by syz-executor.5/21564: #0: ffff8880a8bb30a0 (&p->lock){+.+.}, at: seq_read+0x6b/0xdb0 fs/seq_file.c:161 stack backtrace: CPU: 1 PID: 21564 Comm: syz-executor.5 Not tainted 5.5.0-rc6-syzkaller #0 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+0x1fb/0x318 lib/dump_stack.c:118 print_circular_bug+0xc3f/0xe70 kernel/locking/lockdep.c:1685 check_noncircular+0x206/0x3a0 kernel/locking/lockdep.c:1809 check_prev_add kernel/locking/lockdep.c:2476 [inline] check_prevs_add kernel/locking/lockdep.c:2581 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2971 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3955 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4485 __mutex_lock_common+0x16e/0x2f30 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_killable_nested+0x1b/0x30 kernel/locking/mutex.c:1133 lock_trace fs/proc/base.c:406 [inline] proc_pid_stack+0xd9/0x200 fs/proc/base.c:450 proc_single_show+0xe7/0x180 fs/proc/base.c:756 seq_read+0x4d8/0xdb0 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:714 [inline] do_iter_read+0x4a2/0x5b0 fs/read_write.c:935 vfs_readv fs/read_write.c:997 [inline] do_preadv+0x178/0x290 fs/read_write.c:1089 __do_sys_preadv fs/read_write.c:1139 [inline] __se_sys_preadv fs/read_write.c:1134 [inline] __x64_sys_preadv+0x9e/0xb0 fs/read_write.c:1134 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45af49 Code: ad b6 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 b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f893d1e0c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000045af49 RDX: 0000000000000332 RSI: 00000000200017c0 RDI: 0000000000000004 RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f893d1e16d4 R13: 00000000004c954e R14: 00000000004e2220 R15: 00000000ffffffff --- This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot.