Re: general protection fault in account_system_index_time

From: Eric Biggers
Date: Sun May 13 2018 - 17:39:04 EST

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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@xxxxxxxxxxxxxxxxxxxxxxxxx
> 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: ï 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@xxxxxxxxxxxxxxxxx
>
> 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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