general protection fault in account_system_index_time

syzbot
2018-03-28T07:01:08Z

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@syzkaller.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: \x01�\x02 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@googlegroups.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
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug
report.
Note: all commands must start from beginning of the line in the email body.