Date:   Sun, 13 May 2018 14:40:52 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     syzbot <syzbot+bab86ea70f6f74bd9199@...kaller.appspotmail.com>
Cc:     fweisbec@...il.com, linux-kernel@...r.kernel.org, mingo@...nel.org,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de,
        Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
Subject: Re: general protection fault in account_system_index_time

On Wed, Mar 28, 2018 at 12:01:02AM -0700, syzbot wrote:
> 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.
> 
> syzbot will keep track of this bug report.
> If you forgot to add the Reported-by tag, once the fix for this bug is
> merged
> into any tree, please reply to this email with:
> #syz fix: exact-commit-title

This was fixed by commit ae4745730cf8e69:

#syz fix: net: Fix untag for vlan packets without ethernet header

- Eric

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