Date:   Wed, 28 Mar 2018 00:01:02 -0700
From:   syzbot <syzbot+bab86ea70f6f74bd9199@...kaller.appspotmail.com>
To:     fweisbec@...il.com, linux-kernel@...r.kernel.org, mingo@...nel.org,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de
Subject: general protection fault in account_system_index_time

Hello,

syzbot hit the following crash on upstream commit
3eb2ce825ea1ad89d20f7a3b5780df850e4be274 (Sun Mar 25 22:44:30 2018 +0000)
Linux 4.16-rc7
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=bab86ea70f6f74bd9199

So far this crash happened 2 times on upstream.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=4644092092874752
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=4728333984071680
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=6080200710291456
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=-8440362230543204781
compiler: gcc (GCC) 7.1.1 20170620

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+bab86ea70f6f74bd9199@...kaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

IPVS: ftp: loaded support on port[0] = 21
kasan: CONFIG_KASAN_INLINE enabled
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 164097 Comm: .�. Not tainted 4.16.0-rc7+ #368
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
RIP: 0010:get_running_cputimer include/linux/sched/cputime.h:85 [inline]
RIP: 0010:account_group_system_time include/linux/sched/cputime.h:149  
[inline]
RIP: 0010:account_system_index_time+0xdd/0x5e0 kernel/sched/cputime.c:172
RSP: 0018:ffff8801db207930 EFLAGS: 00010006
RAX: 0002810100028101 RBX: ffff8801b22d0300 RCX: 0000502020005047
RDX: dffffc0000000000 RSI: 00000000000f4240 RDI: 0002810100028239
RBP: ffff8801db207a10 R08: 0000000000028101 R09: fffffbfff0f6a2bb
R10: ffff8801db2079e8 R11: fffffbfff0f6a2ba R12: 1ffff1003b640f29
R13: 000000000002c5c0 R14: 00000000000f4240 R15: 0000000000000002
FS:  00000000019fd880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000421d60 CR3: 00000001b1963003 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  <IRQ>
  account_system_time+0x7f/0xb0 kernel/sched/cputime.c:203
  account_process_tick+0xd4/0x3e0 kernel/sched/cputime.c:502
  update_process_times+0x23/0x60 kernel/time/timer.c:1634
  tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
  tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1194
  __run_hrtimer kernel/time/hrtimer.c:1349 [inline]
  __hrtimer_run_queues+0x39c/0xec0 kernel/time/hrtimer.c:1411
  hrtimer_interrupt+0x2a5/0x6f0 kernel/time/hrtimer.c:1469
  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
  smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:857
  </IRQ>
Code: ea 03 80 3c 02 00 0f 85 8b 04 00 00 48 8b 83 f8 06 00 00 48 ba 00 00  
00 00 00 fc ff df 48 8d b8 38 01 00 00 48 89 f9 48 c1 e9 03 <0f> b6 14 11  
48 89 f9 83 e1 07 38 ca 7f 08 84 d2 0f 85 90 03 00
RIP: __read_once_size include/linux/compiler.h:188 [inline] RSP:  
ffff8801db207930
RIP: get_running_cputimer include/linux/sched/cputime.h:85 [inline] RSP:  
ffff8801db207930
RIP: account_group_system_time include/linux/sched/cputime.h:149 [inline]  
RSP: ffff8801db207930
RIP: account_system_index_time+0xdd/0x5e0 kernel/sched/cputime.c:172 RSP:  
ffff8801db207930

======================================================
WARNING: possible circular locking dependency detected
4.16.0-rc7+ #368 Not tainted
------------------------------------------------------
rcu_sched/8 is trying to acquire lock:
  ((console_sem).lock){..-.}, at: [<0000000011a525fb>]  
down_trylock+0x13/0x70 kernel/locking/semaphore.c:136

but task is already holding lock:
  (&rq->lock){-.-.}, at: [<000000004637b5ed>] rq_lock_irqsave  
kernel/sched/sched.h:1744 [inline]
  (&rq->lock){-.-.}, at: [<000000004637b5ed>] load_balance+0xb10/0x34c0  
kernel/sched/fair.c:8548

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+0x2a/0x40 kernel/locking/spinlock.c:144
        rq_lock kernel/sched/sched.h:1760 [inline]
        task_fork_fair+0x7a/0x690 kernel/sched/fair.c:9471
        sched_fork+0x450/0xc10 kernel/sched/core.c:2405
        copy_process.part.38+0x17c9/0x4bd0 kernel/fork.c:1763
        copy_process kernel/fork.c:1606 [inline]
        _do_fork+0x1f7/0xf70 kernel/fork.c:2087
        kernel_thread+0x34/0x40 kernel/fork.c:2146
        rest_init+0x22/0xf0 init/main.c:403
        start_kernel+0x7f1/0x819 init/main.c:717
        x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378
        x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359
        secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:239

-> #1 (&p->pi_lock){-.-.}:
        __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
        _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
        try_to_wake_up+0xbc/0x15f0 kernel/sched/core.c:1989
        wake_up_process+0x10/0x20 kernel/sched/core.c:2152
        __up.isra.0+0x1cc/0x2c0 kernel/locking/semaphore.c:262
        up+0x13b/0x1d0 kernel/locking/semaphore.c:187
        __up_console_sem+0xb2/0x1a0 kernel/printk/printk.c:242
        console_unlock+0x5af/0xfb0 kernel/printk/printk.c:2417
        do_con_write+0x106e/0x1f70 drivers/tty/vt/vt.c:2433
        con_write+0x25/0xb0 drivers/tty/vt/vt.c:2782
        process_output_block drivers/tty/n_tty.c:579 [inline]
        n_tty_write+0x5ef/0xec0 drivers/tty/n_tty.c:2308
        do_tty_write drivers/tty/tty_io.c:958 [inline]
        tty_write+0x3fa/0x840 drivers/tty/tty_io.c:1042
        __vfs_write+0xef/0x970 fs/read_write.c:480
        vfs_write+0x189/0x510 fs/read_write.c:544
        SYSC_write fs/read_write.c:589 [inline]
        SyS_write+0xef/0x220 fs/read_write.c:581
        do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
        entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #0 ((console_sem).lock){..-.}:
        lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
        __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
        _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
        down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
        __down_trylock_console_sem+0xa2/0x1e0 kernel/printk/printk.c:225
        console_trylock+0x15/0x70 kernel/printk/printk.c:2229
        console_trylock_spinning kernel/printk/printk.c:1643 [inline]
        vprintk_emit+0x5b5/0xb90 kernel/printk/printk.c:1906
        vprintk_default+0x28/0x30 kernel/printk/printk.c:1947
        vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
        printk+0xaa/0xca kernel/printk/printk.c:1980
        kasan_die_handler+0x31/0x3f arch/x86/mm/kasan_init_64.c:247
        notifier_call_chain+0x136/0x2c0 kernel/notifier.c:93
        __atomic_notifier_call_chain kernel/notifier.c:183 [inline]
        atomic_notifier_call_chain+0x77/0x140 kernel/notifier.c:193
        notify_die+0x18c/0x280 kernel/notifier.c:549
        do_general_protection+0x331/0x3e0 arch/x86/kernel/traps.c:558
        general_protection+0x25/0x50 arch/x86/entry/entry_64.S:1150
        task_group kernel/sched/sched.h:1203 [inline]
        can_migrate_task+0xe2/0x1c20 kernel/sched/fair.c:7102
        detach_tasks kernel/sched/fair.c:7251 [inline]
        load_balance+0xdab/0x34c0 kernel/sched/fair.c:8555
        idle_balance kernel/sched/fair.c:8837 [inline]
        pick_next_task_fair+0xe03/0x1630 kernel/sched/fair.c:6757
        pick_next_task kernel/sched/core.c:3286 [inline]
        __schedule+0x4fc/0x1ec0 kernel/sched/core.c:3414
        schedule+0xf5/0x430 kernel/sched/core.c:3499
        schedule_timeout+0x118/0x230 kernel/time/timer.c:1801
        rcu_gp_kthread+0x9dd/0x18e0 kernel/rcu/tree.c:2230
        kthread+0x33c/0x400 kernel/kthread.c:238
        ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406

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 rcu_sched/8:
  #0:  (rcu_read_lock){....}, at: [<0000000024de6645>]  
rcu_read_lock+0x0/0x70 include/linux/compiler.h:188
  #1:  (&rq->lock){-.-.}, at: [<000000004637b5ed>] rq_lock_irqsave  
kernel/sched/sched.h:1744 [inline]
  #1:  (&rq->lock){-.-.}, at: [<000000004637b5ed>] load_balance+0xb10/0x34c0  
kernel/sched/fair.c:8548
  #2:  (rcu_read_lock){....}, at: [<00000000c60bf25c>] rcu_read_unlock  
include/linux/rcupdate.h:682 [inline]
  #2:  (rcu_read_lock){....}, at: [<00000000c60bf25c>]  
atomic_notifier_call_chain+0x0/0x140 kernel/notifier.c:184

stack backtrace:
CPU: 1 PID: 8 Comm: rcu_sched Not tainted 4.16.0-rc7+ #368
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x24d lib/dump_stack.c:53
  print_circular_bug.isra.38+0x2cd/0x2dc kernel/locking/lockdep.c:1223
  check_prev_add kernel/locking/lockdep.c:1863 [inline]
  check_prevs_add kernel/locking/lockdep.c:1976 [inline]
  validate_chain kernel/locking/lockdep.c:2417 [inline]
  __lock_acquire+0x30a8/0x3e00 kernel/locking/lockdep.c:3431
  lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
  _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
  down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
  __down_trylock_console_sem+0xa2/0x1e0 kernel/printk/printk.c:225
  console_trylock+0x15/0x70 kernel/printk/printk.c:2229
  console_trylock_spinning kernel/printk/printk.c:1643 [inline]
  vprintk_emit+0x5b5/0xb90 kernel/printk/printk.c:1906
  vprintk_default+0x28/0x30 kernel/printk/printk.c:1947
  vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
  printk+0xaa/0xca kernel/printk/printk.c:1980
  kasan_die_handler+0x31/0x3f arch/x86/mm/kasan_init_64.c:247
  notifier_call_chain+0x136/0x2c0 kernel/notifier.c:93
  __atomic_notifier_call_chain kernel/notifier.c:183 [inline]
  atomic_notifier_call_chain+0x77/0x140 kernel/notifier.c:193
  notify_die+0x18c/0x280 kernel/notifier.c:549
  do_general_protection+0x331/0x3e0 arch/x86/kernel/traps.c:558
  general_protection+0x25/0x50 arch/x86/entry/entry_64.S:1150
RIP: 0010:task_group kernel/sched/sched.h:1203 [inline]
RIP: 0010:can_migrate_task+0xe2/0x1c20 kernel/sched/fair.c:7102
RSP: 0018:ffff8801d9af6c88 EFLAGS: 00010006
RAX: dffffc0000000000 RBX: 0002810100028101 RCX: ffff8801d9af7098
RDX: ffff8801d9af6d30 RSI: 000050202000503c RDI: 00028101000281e1
RBP: ffff8801d9af6d58 R08: 1ffff1003b35ed9a R09: ffff88021fff8048
R10: 0000000000000001 R11: ffff88021fff805d R12: ffff8801b22d0300
R13: ffffffff87d5df20 R14: ffff8801b22d0300 R15: ffff8801b22d03f0
  detach_tasks kernel/sched/fair.c:7251 [inline]
  load_balance+0xdab/0x34c0 kernel/sched/fair.c:8555
  idle_balance kernel/sched/fair.c:8837 [inline]
  pick_next_task_fair+0xe03/0x1630 kernel/sched/fair.c:6757
  pick_next_task kernel/sched/core.c:3286 [inline]
  __schedule+0x4fc/0x1ec0 kernel/sched/core.c:3414
  schedule+0xf5/0x430 kernel/sched/core.c:3499
  schedule_timeout+0x118/0x230 kernel/time/timer.c:1801
  rcu_gp_kthread+0x9dd/0x18e0 kernel/rcu/tree.c:2230
  ? __schedule+0x1
Lost 10 message(s)!
---[ end trace 948581b189460493 ]---
general protection fault: 0000 [#2] SMP KASAN
Dumping ftrace buffer:


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@...glegroups.com.

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