Message-ID: <alpine.DEB.2.21.1811190921190.9459@nanos.tec.linutronix.de>
Date:   Mon, 19 Nov 2018 09:23:03 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     syzbot <syzbot+119ba87189432ead09b4@...kaller.appspotmail.com>
cc:     Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>, mingo@...hat.com,
        syzkaller-bugs@...glegroups.com, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: WARNING in enqueue_task_dl

Adding scheduler folks

On Sun, 18 Nov 2018, syzbot wrote:

> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    1ce80e0fe98e Merge tag 'fsnotify_for_v4.20-rc3' of git://g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14ddbb0b400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d86f24333880b605
> dashboard link: https://syzkaller.appspot.com/bug?extid=119ba87189432ead09b4
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13e9e015400000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+119ba87189432ead09b4@...kaller.appspotmail.com
> 
> IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
> IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
> 8021q: adding VLAN 0 to HW filter on device team0
> hrtimer: interrupt took 33411 ns
> sched: DL replenish lagged too much
> WARNING: CPU: 1 PID: 6351 at kernel/sched/deadline.c:628
> enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504
> PM: Basic memory bitmaps freed
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 1 PID: 6351 Comm: syz-executor0 Not tainted 4.20.0-rc2+ #338
> 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+0x244/0x39d lib/dump_stack.c:113
> panic+0x2ad/0x55c kernel/panic.c:188
> __warn.cold.8+0x20/0x45 kernel/panic.c:540
> report_bug+0x254/0x2d0 lib/bug.c:186
> fixup_bug arch/x86/kernel/traps.c:178 [inline]
> do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
> do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
> invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
> RIP: 0010:enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504
> Code: ff 48 8b 8d c8 fe ff ff 48 c1 e6 2a 4c 8b 9d d0 fe ff ff 8b 95 d8 fe ff
> ff 48 8b 85 e0 fe ff ff e9 16 e4 ff ff e8 16 d0 ea ff <0f> 0b e9 17 f1 ff ff
> 48 8b bd e8 fe ff ff 4c 89 95 c8 fe ff ff 48
> RSP: 0018:ffff8881ba39fa18 EFLAGS: 00010002
> RAX: 0000000000000000 RBX: ffff8881b9d6c000 RCX: ffff8881b9d6c278
> RDX: ffff8881b9d6c03c RSI: 0000000000000002 RDI: ffff8881daf2d710
> RBP: ffff8881ba39fb78 R08: 0000000000000001 R09: ffff8881daf00000
> R10: 0000001a4d4f1987 R11: ffff8881daf2db3b R12: 1ffff11037473f4e
> R13: ffff8881b9d6c2cc R14: ffff8881daf2ccc0 R15: ffff8881daf2ccc0
> enqueue_task+0x184/0x390 kernel/sched/core.c:730
> __sched_setscheduler+0xe99/0x2190 kernel/sched/core.c:4336
> sched_setattr kernel/sched/core.c:4394 [inline]
> __do_sys_sched_setattr kernel/sched/core.c:4570 [inline]
> __se_sys_sched_setattr kernel/sched/core.c:4549 [inline]
> __x64_sys_sched_setattr+0x1b2/0x2f0 kernel/sched/core.c:4549
> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x457569
> Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f05ce0a2c78 EFLAGS: 00000246 ORIG_RAX: 000000000000013a
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457569
> RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000000
> RBP: 000000000072bfa0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f05ce0a36d4
> R13: 00000000004c369f R14: 00000000004d5730 R15: 00000000ffffffff
> 
> ======================================================
> WARNING: possible circular locking dependency detected
> 4.20.0-rc2+ #338 Not tainted
> ------------------------------------------------------
> syz-executor0/6351 is trying to acquire lock:
> 00000000b2b97155 ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70
> kernel/locking/semaphore.c:136
> 
> but task is already holding lock:
> 000000004cd5557e (&rq->lock){-.-.}, at: task_rq_lock+0xc5/0x2a0
> kernel/sched/core.c:99
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #2 (&rq->lock){-.-.}:
>       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>       _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
>       rq_lock kernel/sched/sched.h:1126 [inline]
>       task_fork_fair+0xb0/0x6d0 kernel/sched/fair.c:9768
>       sched_fork+0x443/0xba0 kernel/sched/core.c:2359
>       copy_process+0x25b8/0x87a0 kernel/fork.c:1887
>       _do_fork+0x1cb/0x11d0 kernel/fork.c:2216
>       kernel_thread+0x34/0x40 kernel/fork.c:2275
>       rest_init+0x28/0x372 init/main.c:409
>       arch_call_rest_init+0xe/0x1b
>       start_kernel+0x9f0/0xa2b init/main.c:745
>       x86_64_start_reservations+0x2e/0x30 arch/x86/kernel/head64.c:472
>       x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
>       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
> 
> -> #1 (&p->pi_lock){-.-.}:
>       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>       _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
>       try_to_wake_up+0xdc/0x1490 kernel/sched/core.c:1965
>       wake_up_process+0x10/0x20 kernel/sched/core.c:2129
>       __up.isra.1+0x1c0/0x2a0 kernel/locking/semaphore.c:262
>       up+0x13c/0x1c0 kernel/locking/semaphore.c:187
>       __up_console_sem+0xbe/0x1b0 kernel/printk/printk.c:236
>       console_unlock+0x811/0x1190 kernel/printk/printk.c:2432
>       do_con_write+0x1356/0x23b0 drivers/tty/vt/vt.c:2767
>       con_write+0x25/0xc0 drivers/tty/vt/vt.c:3116
>       process_output_block drivers/tty/n_tty.c:593 [inline]
>       n_tty_write+0x6c1/0x11a0 drivers/tty/n_tty.c:2331
>       do_tty_write drivers/tty/tty_io.c:959 [inline]
>       tty_write+0x3f1/0x880 drivers/tty/tty_io.c:1043
>       __vfs_write+0x119/0x9f0 fs/read_write.c:485
>       vfs_write+0x1fc/0x560 fs/read_write.c:549
>       ksys_write+0x101/0x260 fs/read_write.c:598
>       __do_sys_write fs/read_write.c:610 [inline]
>       __se_sys_write fs/read_write.c:607 [inline]
>       __x64_sys_write+0x73/0xb0 fs/read_write.c:607
>       do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>       entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> -> #0 ((console_sem).lock){-.-.}:
>       lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
>       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>       _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
>       down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
>       __down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:219
>       console_trylock+0x15/0xa0 kernel/printk/printk.c:2247
>       console_trylock_spinning kernel/printk/printk.c:1653 [inline]
>       vprintk_emit+0x372/0x990 kernel/printk/printk.c:1921
>       vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
>       vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
>       printk+0xa7/0xcf kernel/printk/printk.c:1997
>       __warn+0x9e/0x1d0 kernel/panic.c:522
>       report_bug+0x254/0x2d0 lib/bug.c:186
>       fixup_bug arch/x86/kernel/traps.c:178 [inline]
>       do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
>       do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
>       invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
>       enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504
>       enqueue_task+0x184/0x390 kernel/sched/core.c:730
>       __sched_setscheduler+0xe99/0x2190 kernel/sched/core.c:4336
>       sched_setattr kernel/sched/core.c:4394 [inline]
>       __do_sys_sched_setattr kernel/sched/core.c:4570 [inline]
>       __se_sys_sched_setattr kernel/sched/core.c:4549 [inline]
>       __x64_sys_sched_setattr+0x1b2/0x2f0 kernel/sched/core.c:4549
>       do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>       entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> other info that might help us debug this:
> 
> Chain exists of:
>  (console_sem).lock --> &p->pi_lock --> &rq->lock
> 
> Possible unsafe locking scenario:
> 
>       CPU0                    CPU1
>       ----                    ----
>  lock(&rq->lock);
>                               lock(&p->pi_lock);
>                               lock(&rq->lock);
>  lock((console_sem).lock);
> 
> *** DEADLOCK ***
> 
> 3 locks held by syz-executor0/6351:
> #0: 000000001a0356c1 (rcu_read_lock){....}, at: __do_sys_sched_setattr
> kernel/sched/core.c:4563 [inline]
> #0: 000000001a0356c1 (rcu_read_lock){....}, at: __se_sys_sched_setattr
> kernel/sched/core.c:4549 [inline]
> #0: 000000001a0356c1 (rcu_read_lock){....}, at:
> __x64_sys_sched_setattr+0x146/0x2f0 kernel/sched/core.c:4549
> #1: 000000000b71b478 (&p->pi_lock){-.-.}, at: task_rq_lock+0x62/0x2a0
> kernel/sched/core.c:97
> #2: 000000004cd5557e (&rq->lock){-.-.}, at: task_rq_lock+0xc5/0x2a0
> kernel/sched/core.c:99
> 
> stack backtrace:
> CPU: 1 PID: 6351 Comm: syz-executor0 Not tainted 4.20.0-rc2+ #338
> 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+0x244/0x39d lib/dump_stack.c:113
> print_circular_bug.isra.35.cold.54+0x1bd/0x27d kernel/locking/lockdep.c:1221
> check_prev_add kernel/locking/lockdep.c:1863 [inline]
> check_prevs_add kernel/locking/lockdep.c:1976 [inline]
> validate_chain kernel/locking/lockdep.c:2347 [inline]
> __lock_acquire+0x3399/0x4c20 kernel/locking/lockdep.c:3341
> lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
> _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
> down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
> __down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:219
> console_trylock+0x15/0xa0 kernel/printk/printk.c:2247
> console_trylock_spinning kernel/printk/printk.c:1653 [inline]
> vprintk_emit+0x372/0x990 kernel/printk/printk.c:1921
> vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
> vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
> printk+0xa7/0xcf kernel/printk/printk.c:1997
> __warn+0x9e/0x1d0 kernel/panic.c:522
> report_bug+0x254/0x2d0 lib/bug.c:186
> fixup_bug arch/x86/kernel/traps.c:178 [inline]
> do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
> do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
> invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
> RIP: 0010:enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504
> Code: ff 48 8b 8d c8 fe ff ff 48 c1 e6 2a 4c 8b 9d d0 fe ff ff 8b 95 d8 fe ff
> ff 48 8b 85 e0 fe ff ff e9 16 e4 ff ff e8 16 d0 ea ff <0f> 0b e9 17 f1 ff ff
> 48 8b bd e8 fe ff ff 4c 89 95 c8 fe ff ff 48
> RSP: 0018:ffff8881ba39fa18 EFLAGS: 00010002
> RAX: 0000000000000000 RBX: ffff8881b9d6c000 RCX: ffff8881b9d6c278
> RDX: ffff8881b9d6c03c RSI: 0000000000000002 RDI: ffff8881daf2d710
> RBP: ffff8881ba39fb78 R08: 0000000000000001 R09: ffff8881daf00000
> R10: 0000001a4d4f1987 R11: ffff8881daf2db3b R12: 1ffff11037473f4e
> R13: ffff8881b9d6c2cc R14: ffff8881daf2ccc0 R15: ffff8881daf2ccc0
> enqueue_task+0x184/0x390 kernel/sched/core.c:730
> __sched_setscheduler+0xe99/0x2190 kernel/sched/core.c:4336
> sched_setattr kernel/sched/core.c:4394 [inline]
> __do_sys_sched_setattr kernel/sched/core.c:4570 [inline]
> __se_sys_sched_setattr kernel/sched/core.c:4549 [inline]
> __x64_sys_sched_setattr+0x1b2/0x2f0 kernel/sched/core.c:4549
> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x457569
> Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f05ce0a2c78 EFLAGS: 00000246 ORIG_RAX: 000000000000013a
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457569
> RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000000
> RBP: 000000000072bfa0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f05ce0a36d4
> R13: 00000000004c369f R14: 00000000004d5730 R15: 00000000ffffffff
> Shutting down cpus with NMI
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
> 
> 
> ---
> 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@...glegroups.com.
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

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