Date:   Wed, 20 Dec 2017 08:03:01 -0800
From:   syzbot 
        <bot+df206d897b7957e7c7a8c34e18c39a24d5256877@...kaller.appspotmail.com>
To:     akpm@...ux-foundation.org, jglisse@...hat.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, mingo@...nel.org,
        paulmck@...ux.vnet.ibm.com, syzkaller-bugs@...glegroups.com,
        vegard.nossum@...cle.com
Subject: general protection fault in __schedule

Hello,

syzkaller hit the following crash on  
7dc9f647127d6955ffacaf51cb6a627b31dceec2
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


kvm: KVM_SET_TSS_ADDR need to be called before entering vcpu
kasan: CONFIG_KASAN_INLINE enabled
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: 1 PID: 3151 Comm: syzkaller527934 Not tainted  
4.15.0-rc4-next-20171220+ #77
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__fire_sched_out_preempt_notifiers kernel/sched/core.c:2550  
[inline]
RIP: 0010:fire_sched_out_preempt_notifiers kernel/sched/core.c:2558 [inline]
RIP: 0010:prepare_task_switch kernel/sched/core.c:2594 [inline]
RIP: 0010:context_switch kernel/sched/core.c:2765 [inline]
RIP: 0010:__schedule+0xdf0/0x2060 kernel/sched/core.c:3376
RSP: 0018:ffff8801c93a7068 EFLAGS: 00010806
RAX: 1bd5a00000000022 RBX: ffff8801db32c900 RCX: ffffffff810caeaf
RDX: 0000000000000000 RSI: 0000000000000000 RDI: dead000000000110
RBP: ffff8801c93a7238 R08: 0000000000000000 R09: 1ffff10039274de1
R10: ffff8801c93a6ed0 R11: 0000000000000001 R12: ffff8801d3948040
R13: dead000000000100 R14: dffffc0000000000 R15: ffff8801c9ca20c0
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001000 CR3: 0000000006422006 CR4: 00000000001626e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  preempt_schedule_common+0x22/0x60 kernel/sched/core.c:3515
  _cond_resched+0x1d/0x30 kernel/sched/core.c:4852
  __wait_for_common kernel/sched/completion.c:107 [inline]
  wait_for_common kernel/sched/completion.c:123 [inline]
  wait_for_completion+0xa5/0x770 kernel/sched/completion.c:144
  __synchronize_srcu+0x1ad/0x260 kernel/rcu/srcutree.c:925
  synchronize_srcu_expedited kernel/rcu/srcutree.c:950 [inline]
  synchronize_srcu+0x1a3/0x570 kernel/rcu/srcutree.c:1001
  __mmu_notifier_release+0x357/0x690 mm/mmu_notifier.c:102
  mmu_notifier_release include/linux/mmu_notifier.h:225 [inline]
  exit_mmap+0x3ff/0x500 mm/mmap.c:3009
  __mmput kernel/fork.c:965 [inline]
  mmput+0x223/0x6c0 kernel/fork.c:986
  exit_mm kernel/exit.c:544 [inline]
  do_exit+0x90a/0x1ad0 kernel/exit.c:856
  do_group_exit+0x149/0x400 kernel/exit.c:972
  SYSC_exit_group kernel/exit.c:983 [inline]
  SyS_exit_group+0x1d/0x20 kernel/exit.c:981
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x43ee88
RSP: 002b:00007ffc8be9bb08 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043ee88
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000006ca018 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401bb0
R13: 0000000000401c40 R14: 0000000000000000 R15: 0000000000000000
Code: 08 4c 89 e8 48 c1 e8 03 42 80 3c 30 00 0f 85 ce 0f 00 00 4d 8b 6d 00  
4d 85 ed 0f 84 72 f9 ff ff 49 8d 7d 10 48 89 f8 48 c1 e8 03 <42> 80 3c 30  
00 74 ac eb a5 49 8d bc 24 28 04 00 00 48 b8 00 00
RIP: __fire_sched_out_preempt_notifiers kernel/sched/core.c:2550 [inline]  
RSP: ffff8801c93a7068
RIP: fire_sched_out_preempt_notifiers kernel/sched/core.c:2558 [inline]  
RSP: ffff8801c93a7068
RIP: prepare_task_switch kernel/sched/core.c:2594 [inline] RSP:  
ffff8801c93a7068
RIP: context_switch kernel/sched/core.c:2765 [inline] RSP: ffff8801c93a7068
RIP: __schedule+0xdf0/0x2060 kernel/sched/core.c:3376 RSP: ffff8801c93a7068

======================================================
WARNING: possible circular locking dependency detected
4.15.0-rc4-next-20171220+ #77 Not tainted
------------------------------------------------------
syzkaller527934/3151 is trying to acquire lock:
  ((console_sem).lock){..-.}, at: [<00000000e19404b5>]  
down_trylock+0x13/0x70 kernel/locking/semaphore.c:136

but task is already holding lock:
  (&rq->lock){-.-.}, at: [<000000001c39040b>] rq_lock  
kernel/sched/sched.h:1766 [inline]
  (&rq->lock){-.-.}, at: [<000000001c39040b>] __schedule+0x24e/0x2060  
kernel/sched/core.c:3313

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:1766 [inline]
        task_fork_fair+0x7a/0x690 kernel/sched/fair.c:9448
        sched_fork+0x435/0xc00 kernel/sched/core.c:2405
        copy_process.part.37+0x1758/0x4b60 kernel/fork.c:1770
        copy_process kernel/fork.c:1613 [inline]
        _do_fork+0x1f7/0xf70 kernel/fork.c:2094
        kernel_thread+0x34/0x40 kernel/fork.c:2153
        rest_init+0x22/0xf0 init/main.c:402
        start_kernel+0x7f1/0x819 init/main.c:716
        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:237

-> #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/0x1600 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:245
        console_unlock+0x538/0xd70 kernel/printk/printk.c:2248
        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:2302
        do_tty_write drivers/tty/tty_io.c:949 [inline]
        tty_write+0x3fa/0x840 drivers/tty/tty_io.c:1033
        __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
        entry_SYSCALL_64_fastpath+0x1f/0x96

-> #0 ((console_sem).lock){..-.}:
        lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3914
        __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:228
        console_trylock+0x15/0x100 kernel/printk/printk.c:2065
        vprintk_emit+0x49b/0x590 kernel/printk/printk.c:1756
        vprintk_default+0x28/0x30 kernel/printk/printk.c:1796
        vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
        printk+0xaa/0xca kernel/printk/printk.c:1829
        kasan_die_handler+0x31/0x3f arch/x86/mm/kasan_init_64.c:242
        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:557
        general_protection+0x2c/0x60 arch/x86/entry/entry_64.S:1242
        __fire_sched_out_preempt_notifiers kernel/sched/core.c:2550 [inline]
        fire_sched_out_preempt_notifiers kernel/sched/core.c:2558 [inline]
        prepare_task_switch kernel/sched/core.c:2594 [inline]
        context_switch kernel/sched/core.c:2765 [inline]
        __schedule+0xdf0/0x2060 kernel/sched/core.c:3376
        preempt_schedule_common+0x22/0x60 kernel/sched/core.c:3515
        _cond_resched+0x1d/0x30 kernel/sched/core.c:4852
        __wait_for_common kernel/sched/completion.c:107 [inline]
        wait_for_common kernel/sched/completion.c:123 [inline]
        wait_for_completion+0xa5/0x770 kernel/sched/completion.c:144
        __synchronize_srcu+0x1ad/0x260 kernel/rcu/srcutree.c:925
        synchronize_srcu_expedited kernel/rcu/srcutree.c:950 [inline]
        synchronize_srcu+0x1a3/0x570 kernel/rcu/srcutree.c:1001
        __mmu_notifier_release+0x357/0x690 mm/mmu_notifier.c:102
        mmu_notifier_release include/linux/mmu_notifier.h:225 [inline]
        exit_mmap+0x3ff/0x500 mm/mmap.c:3009
        __mmput kernel/fork.c:965 [inline]
        mmput+0x223/0x6c0 kernel/fork.c:986
        exit_mm kernel/exit.c:544 [inline]
        do_exit+0x90a/0x1ad0 kernel/exit.c:856
        do_group_exit+0x149/0x400 kernel/exit.c:972
        SYSC_exit_group kernel/exit.c:983 [inline]
        SyS_exit_group+0x1d/0x20 kernel/exit.c:981
        entry_SYSCALL_64_fastpath+0x1f/0x96

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 ***

2 locks held by syzkaller527934/3151:
  #0:  (&rq->lock){-.-.}, at: [<000000001c39040b>] rq_lock  
kernel/sched/sched.h:1766 [inline]
  #0:  (&rq->lock){-.-.}, at: [<000000001c39040b>] __schedule+0x24e/0x2060  
kernel/sched/core.c:3313
  #1:  (rcu_read_lock){....}, at: [<00000000a6163887>] rcu_read_unlock  
include/linux/rcupdate.h:682 [inline]
  #1:  (rcu_read_lock){....}, at: [<00000000a6163887>]  
atomic_notifier_call_chain+0x0/0x140 kernel/notifier.c:184

stack backtrace:
CPU: 1 PID: 3151 Comm: syzkaller527934 Not tainted  
4.15.0-rc4-next-20171220+ #77
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+0x194/0x257 lib/dump_stack.c:53
  print_circular_bug.isra.37+0x2cd/0x2dc kernel/locking/lockdep.c:1218
  check_prev_add kernel/locking/lockdep.c:1858 [inline]
  check_prevs_add kernel/locking/lockdep.c:1971 [inline]
  validate_chain kernel/locking/lockdep.c:2412 [inline]
  __lock_acquire+0x30a8/0x3e00 kernel/locking/lockdep.c:3426
  lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3914
  __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:228
  console_trylock+0x15/0x100 kernel/printk/printk.c:2065
  vprintk_emit+0x49b/0x590 kernel/printk/printk.c:1756
  vprintk_default+0x28/0x30 kernel/printk/printk.c:1796
  vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
  printk+0xaa/0xca kernel/printk/printk.c:1829
  kasan_die_handler+0x31/0x3f arch/x86/mm/kasan_init_64.c:242
  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:557
  general_protection+0x2c/0x60 arch/x86/entry/entry_64.S:1242
RIP: 0010:__fire_sched_out_preempt_notifiers kernel/sched/core.c:2550  
[inline]
RIP: 0010:fire_sched_out_preempt_notifiers kernel/sched/core.c:2558 [inline]
RIP: 0010:prepare_task_switch kernel/sched/core.c:2594 [inline]
RIP: 0010:context_switch kernel/sched/core.c:2765 [inline]
RIP: 0010:__schedule+0xdf0/0x2060 kernel/sched/core.c:3376
RSP: 0018:ffff8801c93a7068 EFLAGS: 00010806
RAX: 1bd5a00000000022 RBX: ffff8801db32c900 RCX: ffffffff810caeaf
RDX: 0000000000000000 RSI: 0000000000000000 RDI: dead000000000110
RBP: ffff8801c93a7238 R08: 0000000000000000 R09: 1ffff10039274de1
R10: ffff8801c93a6ed0 R11: 0000000000000001 R12: ffff8801d3948040
R13: dead000000000100 R14: dffffc0000000000 R15: ffff8801c9ca20c0
  preempt_schedule_common+0x22/0x60 kernel/sched/core.c:3515
  _cond_resched+0x1d/0x30 kernel/sched/core.c:4852
  __wait_for_common kernel/sched/completion.c:107 [inline]
  wait_for_common kernel/sched/completion.c:123 [inline]
  wait_for_completion+0xa5/0x770 kernel/sched/completion.c:144
  __synchronize_srcu+0x1ad/0x260 kernel/rcu/srcutree.c:925
  synchronize_srcu_expedited kernel/rcu/srcutree.c:950 [inline]
  synchronize_srcu+0x1a3/0x570 kernel/rcu/srcutree.c:1001
  __mmu_notifier_release+0x357/0x690 mm/mmu_notifier.c:102
  mmu_notifier_release include/linux/mmu_notifier.h:225 [inline]
  exit_mmap+0x3ff/0x500 mm/mmap.c:3009
  __mmput kernel/fork.c:965 [inline]
  mmput+0x223/0x6c0 kernel/fork.c:986
  exit_mm kernel/exit.c:544 [inline]
  do_exit+0x90a/0x1ad0 kernel/exit.c:856
  do_group_exit+0x149/0x400 kernel/exit.c:972
  SYSC_exit_group kernel/exit.c:983 [inline]
  SyS_exit_group+0x1d/0x20 kernel/exit.c:981
  entry_SYSCALL_64_fastpath+0
Lost 8 message(s)!
---[ end trace 5970b16ce521c1ec ]---


---
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.
Please credit me with: Reported-by: syzbot <syzkaller@...glegroups.com>

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Once a fix for this bug is merged into any tree, reply to this email with:
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Note: if the crash happens again, it will cause creation of a new bug  
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