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[209.132.180.67]) by mx.google.com with ESMTP id a4si1047279otq.98.2020.02.27.00.40.36; Thu, 27 Feb 2020 00:40:47 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=appspotmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728614AbgB0IjO (ORCPT + 99 others); Thu, 27 Feb 2020 03:39:14 -0500 Received: from mail-il1-f199.google.com ([209.85.166.199]:41198 "EHLO mail-il1-f199.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728440AbgB0IjO (ORCPT ); Thu, 27 Feb 2020 03:39:14 -0500 Received: by mail-il1-f199.google.com with SMTP id k9so4379743ili.8 for ; Thu, 27 Feb 2020 00:39:12 -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=q0lYrwRVdnUGvEQaooBsjU/1Z2nf/gS3i3kKTs6syaQ=; b=VGlvLR5LW9riW1la57bxDIJ+kmm4TKR96JavvG+n27uSnlCAe/uY/DMgw7R1+Bka+i cQF1tIcMLv4BNxH9rEzeMu3bm/zlfMQfI3CZh9yhTfTkWvBgkRSLxLBDubnVdHNjIP+J 8doQrhFv9Zw7che1xyeAUx1HO6v1tl4y1dQupfgPFF8M5KpQ0xZguetpnpd6fHCPJj3B 3DA4eryccfDyO/9STlHRSkmlvRRDnYmtkYEekM7bN43eAiC0WiShRjsld+BOGMcVsYuF F+bk9G+048lYAkOsD97yulNN5GVR0pzcNHDHGuPJkP5F+iuP/dhJei7SaxSrrY9NdhiL y01g== X-Gm-Message-State: APjAAAWRwwTl86rvJWkq1RxVCBmZLWaRVT4VYdUIfca5Dc1EGQBYSfK5 tcdXhGg5m5aMdKbI7/8NLkUFrD4QZ8jAtVgcxX7hj1NtZNj+ MIME-Version: 1.0 X-Received: by 2002:a92:8dc3:: with SMTP id w64mr3460034ill.68.1582792752123; Thu, 27 Feb 2020 00:39:12 -0800 (PST) Date: Thu, 27 Feb 2020 00:39:12 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <000000000000be57bf059f8aa7b9@google.com> Subject: possible deadlock in tty_unthrottle From: syzbot To: gregkh@linuxfoundation.org, jslaby@suse.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, syzbot found the following crash on: HEAD commit: f8788d86 Linux 5.6-rc3 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1102d22de00000 kernel config: https://syzkaller.appspot.com/x/.config?x=5d2e033af114153f dashboard link: https://syzkaller.appspot.com/bug?extid=26183d9746e62da329b8 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+26183d9746e62da329b8@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected 5.6.0-rc3-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/20336 is trying to acquire lock: ffff8880a2e952a0 (&tty->termios_rwsem){++++}, at: tty_unthrottle+0x22/0x100 drivers/tty/tty_ioctl.c:136 but task is already holding lock: ffffffff89462e70 (sel_lock){+.+.}, at: paste_selection+0x118/0x470 drivers/tty/vt/selection.c:374 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (sel_lock){+.+.}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 __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 set_selection_kernel+0x3b8/0x18a0 drivers/tty/vt/selection.c:217 set_selection_user+0x63/0x80 drivers/tty/vt/selection.c:181 tioclinux+0x103/0x530 drivers/tty/vt/vt.c:3050 vt_ioctl+0x3f1/0x3a30 drivers/tty/vt/vt_ioctl.c:364 tty_ioctl+0xee6/0x15c0 drivers/tty/tty_io.c:2660 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl fs/ioctl.c:763 [inline] __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl+0x113/0x190 fs/ioctl.c:770 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:770 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (console_lock){+.+.}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 console_lock+0x46/0x70 kernel/printk/printk.c:2289 con_flush_chars+0x50/0x650 drivers/tty/vt/vt.c:3223 n_tty_write+0xeae/0x1200 drivers/tty/n_tty.c:2350 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x5a1/0x950 drivers/tty/tty_io.c:1046 __vfs_write+0xb8/0x740 fs/read_write.c:494 vfs_write+0x270/0x580 fs/read_write.c:558 ksys_write+0x117/0x220 fs/read_write.c:611 __do_sys_write fs/read_write.c:623 [inline] __se_sys_write fs/read_write.c:620 [inline] __x64_sys_write+0x7b/0x90 fs/read_write.c:620 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&tty->termios_rwsem){++++}: check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2970 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3954 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 down_write+0x57/0x140 kernel/locking/rwsem.c:1534 tty_unthrottle+0x22/0x100 drivers/tty/tty_ioctl.c:136 mkiss_receive_buf+0x12aa/0x1340 drivers/net/hamradio/mkiss.c:902 tty_ldisc_receive_buf+0x12f/0x170 drivers/tty/tty_buffer.c:465 paste_selection+0x346/0x470 drivers/tty/vt/selection.c:389 tioclinux+0x121/0x530 drivers/tty/vt/vt.c:3055 vt_ioctl+0x3f1/0x3a30 drivers/tty/vt/vt_ioctl.c:364 tty_ioctl+0xee6/0x15c0 drivers/tty/tty_io.c:2660 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl fs/ioctl.c:763 [inline] __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl+0x113/0x190 fs/ioctl.c:770 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:770 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: &tty->termios_rwsem --> console_lock --> sel_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sel_lock); lock(console_lock); lock(sel_lock); lock(&tty->termios_rwsem); *** DEADLOCK *** 3 locks held by syz-executor.4/20336: #0: ffff8880a2e95090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:267 #1: ffff888097ac10a8 (&buf->lock){+.+.}, at: tty_buffer_lock_exclusive+0x33/0x40 drivers/tty/tty_buffer.c:61 #2: ffffffff89462e70 (sel_lock){+.+.}, at: paste_selection+0x118/0x470 drivers/tty/vt/selection.c:374 stack backtrace: CPU: 1 PID: 20336 Comm: syz-executor.4 Not tainted 5.6.0-rc3-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:1684 check_noncircular+0x206/0x3a0 kernel/locking/lockdep.c:1808 check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2970 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3954 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 down_write+0x57/0x140 kernel/locking/rwsem.c:1534 tty_unthrottle+0x22/0x100 drivers/tty/tty_ioctl.c:136 mkiss_receive_buf+0x12aa/0x1340 drivers/net/hamradio/mkiss.c:902 tty_ldisc_receive_buf+0x12f/0x170 drivers/tty/tty_buffer.c:465 paste_selection+0x346/0x470 drivers/tty/vt/selection.c:389 tioclinux+0x121/0x530 drivers/tty/vt/vt.c:3055 vt_ioctl+0x3f1/0x3a30 drivers/tty/vt/vt_ioctl.c:364 tty_ioctl+0xee6/0x15c0 drivers/tty/tty_io.c:2660 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl fs/ioctl.c:763 [inline] __do_sys_ioctl fs/ioctl.c:772 [inline] __se_sys_ioctl+0x113/0x190 fs/ioctl.c:770 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:770 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c449 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:00007f0ac45bac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f0ac45bb6d4 RCX: 000000000045c449 RDX: 0000000020000140 RSI: 000000000000541c RDI: 0000000000000003 RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000571 R14: 00000000004c7c29 R15: 000000000076bf2c --- 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.