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Date:   Sun, 18 Nov 2018 10:49:03 -0800
Message-ID: <000000000000b5e346057af4da06@google.com>
Subject: WARNING in enqueue_task_dl
From:   syzbot <syzbot+119ba87189432ead09b4@syzkaller.appspotmail.com>
To:     bp@alien8.de, hpa@zytor.com, linux-kernel@vger.kernel.org,
        luto@kernel.org, mingo@redhat.com, syzkaller-bugs@googlegroups.com,
        tglx@linutronix.de, x86@kernel.org
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Sender: linux-kernel-owner@vger.kernel.org
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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@syzkaller.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..


---
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