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SubjectRe: run_timer_softirq gpf. [smc]
On Tue, Mar 21, 2017 at 08:25:39PM +0100, Thomas Gleixner wrote:

> > I just hit this while fuzzing..
> >
> > general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> > CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.11.0-rc2-think+ #1
> > task: ffff88017f0ed440 task.stack: ffffc90000094000
> > RIP: 0010:run_timer_softirq+0x15f/0x700
> > RSP: 0018:ffff880507c03ec8 EFLAGS: 00010086
> > RAX: dead000000000200 RBX: ffff880507dd0d00 RCX: 0000000000000002
> > RDX: ffff880507c03ed0 RSI: 00000000ffffffff RDI: ffffffff8204b3a0
> > RBP: ffff880507c03f48 R08: ffff880507dd12d0 R09: ffff880507c03ed8
> > R10: ffff880507dd0db0 R11: 0000000000000000 R12: ffffffff8215cc38
> > R13: ffff880507c03ed0 R14: ffffffff82005188 R15: ffff8804b55491a8
> > FS: 0000000000000000(0000) GS:ffff880507c00000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000000000004 CR3: 0000000005011000 CR4: 00000000001406e0
> > Call Trace:
> > <IRQ>
> > ? clockevents_program_event+0x47/0x120
> > __do_softirq+0xbf/0x5b1
> > irq_exit+0xb5/0xc0
> > smp_apic_timer_interrupt+0x3d/0x50
> > apic_timer_interrupt+0x97/0xa0
> > RIP: 0010:cpuidle_enter_state+0x12e/0x400
> > RSP: 0018:ffffc90000097e40 EFLAGS: 00000202
> > [CONT START] ORIG_RAX: ffffffffffffff10
> > RAX: ffff88017f0ed440 RBX: ffffe8ffffa03cc8 RCX: 0000000000000001
> > RDX: 20c49ba5e353f7cf RSI: 0000000000000001 RDI: ffff88017f0ed440
> > RBP: ffffc90000097e80 R08: 00000000ffffffff R09: 0000000000000008
> > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000005
> > R13: ffffffff820b9338 R14: 0000000000000005 R15: ffffffff820b9320
> > </IRQ>
> > cpuidle_enter+0x17/0x20
> > call_cpuidle+0x23/0x40
> > do_idle+0xfb/0x200
> > cpu_startup_entry+0x71/0x80
> > start_secondary+0x16a/0x210
> > start_cpu+0x14/0x14
> > Code: 8b 05 ce 1b ef 7e 83 f8 03 0f 87 4e 01 00 00 89 c0 49 0f a3 04 24 0f 82 0a 01 00 00 49 8b 07 49 8b 57 08 48 85 c0 48 89 02 74 04 <48> 89 50 08 41 f6 47 2a 20 49 c7 47 08 00 00 00 00 48 89 df 48
>
> The timer which expires has timer->entry.next == POISON2 !
>
> it's a classic list corruption. The
> bad news is that there is no trace of the culprit because that happens when
> some other timer expires after some random amount of time.
>
> If that is reproducible, then please enable debugobjects. That should
> pinpoint the culprit.

It's net/smc. This recently had a similar bug with workqueues.
(https://marc.info/?l=linux-kernel&m=148821582909541) fixed by 637fdbae60d6cb9f6e963c1079d7e0445c86ff7d
so it's probably unsurprising that there are similar issues.


WARNING: CPU: 0 PID: 2430 at lib/debugobjects.c:289 debug_print_object+0x87/0xb0
ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x20
CPU: 0 PID: 2430 Comm: trinity-c4 Not tainted 4.11.0-rc3-think+ #3
Call Trace:
dump_stack+0x68/0x93
__warn+0xcb/0xf0
warn_slowpath_fmt+0x5f/0x80
? debug_check_no_obj_freed+0xd9/0x260
debug_print_object+0x87/0xb0
? work_on_cpu+0xd0/0xd0
debug_check_no_obj_freed+0x219/0x260
? __sk_destruct+0x10d/0x1c0
kmem_cache_free+0x9f/0x370
__sk_destruct+0x10d/0x1c0
sk_destruct+0x20/0x30
__sk_free+0x43/0xa0
sk_free+0x18/0x20
smc_release+0x100/0x1a0 [smc]
sock_release+0x1f/0x80
sock_close+0x12/0x20
__fput+0xf3/0x200
____fput+0xe/0x10
task_work_run+0x85/0xb0
do_exit+0x331/0xd70
__secure_computing+0x9c/0xa0
syscall_trace_enter+0xd1/0x3d0
do_syscall_64+0x15f/0x1d0
entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x7f535f4b19e7
RSP: 002b:00007fff1a0f40e8 EFLAGS: 00000246
ORIG_RAX: 0000000000000008
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f535f4b19e7
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 0000000000000000 R08: 00007f535fb8b000 R09: 00c17c2740a303e4
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff1a0f40f5
R13: 00007f535fb60048 R14: 00007f535fb83ad8 R15: 00007f535fb60000
---[ end trace ee67155de15508db ]---

======================================================
[ INFO: possible circular locking dependency detected ]
4.11.0-rc3-think+ #3 Not tainted
-------------------------------------------------------
trinity-c4/2430 is trying to acquire lock:
(
(console_sem).lock
){-.-...}
, at: [<ffffffff810e6be4>] down_trylock+0x14/0x40

but task is already holding lock:
(
&obj_hash[i].lock
){-.-.-.}
, at: [<ffffffff81515689>] debug_check_no_obj_freed+0xd9/0x260

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3
(
&obj_hash[i].lock
){-.-.-.}
:
lock_acquire+0x102/0x260
_raw_spin_lock_irqsave+0x4c/0x90
__debug_object_init+0x79/0x460
debug_object_init+0x16/0x20
hrtimer_init+0x25/0x1d0
init_dl_task_timer+0x20/0x30
__sched_fork.isra.91+0x9c/0x140
init_idle+0x51/0x240
sched_init+0x4cd/0x547
start_kernel+0x246/0x45d
x86_64_start_reservations+0x2a/0x2c
x86_64_start_kernel+0x178/0x18b
verify_cpu+0x0/0xf1

-> #2
(
&rq->lock
){-.-.-.}
:
lock_acquire+0x102/0x260
_raw_spin_lock+0x41/0x80
task_fork_fair+0x3a/0x100
sched_fork+0x12b/0x2e0
copy_process.part.39+0x65b/0x2080
_do_fork+0xf6/0x770
kernel_thread+0x29/0x30
rest_init+0x22/0x140
start_kernel+0x43c/0x45d
x86_64_start_reservations+0x2a/0x2c
x86_64_start_kernel+0x178/0x18b
verify_cpu+0x0/0xf1

-> #1
(
&p->pi_lock
){-.-.-.}
:
lock_acquire+0x102/0x260
_raw_spin_lock_irqsave+0x4c/0x90
try_to_wake_up+0x40/0x6e0
wake_up_process+0x15/0x20
__up.isra.0+0x4c/0x50
up+0x46/0x50
__up_console_sem+0x37/0x60
console_unlock+0x275/0x5e0
do_con_write.part.22+0x761/0xa20
con_write+0x5c/0x60
n_tty_write+0x1bf/0x490
tty_write+0x1b3/0x320
redirected_tty_write+0x92/0xb0
__do_readv_writev+0x2e5/0x380
do_readv_writev+0x7c/0xc0
vfs_writev+0x3f/0x50
do_writev+0x64/0x100
SyS_writev+0x10/0x20
do_syscall_64+0x66/0x1d0
return_from_SYSCALL_64+0x0/0x7a

-> #0
(
(console_sem).lock
){-.-...}
:
__lock_acquire+0x1134/0x12b0
lock_acquire+0x102/0x260
_raw_spin_lock_irqsave+0x4c/0x90
down_trylock+0x14/0x40
__down_trylock_console_sem+0x2f/0xa0
console_trylock+0x16/0x90
vprintk_emit+0x2ac/0x390
vprintk_default+0x29/0x50
vprintk_func+0x25/0x80
printk+0x52/0x6e
__warn+0x39/0xf0
warn_slowpath_fmt+0x5f/0x80
debug_print_object+0x87/0xb0
debug_check_no_obj_freed+0x219/0x260
kmem_cache_free+0x9f/0x370
__sk_destruct+0x10d/0x1c0
sk_destruct+0x20/0x30
__sk_free+0x43/0xa0
sk_free+0x18/0x20
smc_release+0x100/0x1a0 [smc]
sock_release+0x1f/0x80
sock_close+0x12/0x20
__fput+0xf3/0x200
____fput+0xe/0x10
task_work_run+0x85/0xb0
do_exit+0x331/0xd70
__secure_computing+0x9c/0xa0
syscall_trace_enter+0xd1/0x3d0
do_syscall_64+0x15f/0x1d0
return_from_SYSCALL_64+0x0/0x7a

other info that might help us debug this:

Chain exists of:

(console_sem).lock
-->
&rq->lock
-->
&obj_hash[i].lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(
&obj_hash[i].lock
);
lock(
&rq->lock
);
lock(
&obj_hash[i].lock
);
lock(
(console_sem).lock
);

*** DEADLOCK ***

1 lock held by trinity-c4/2430:
#0:
(
&obj_hash[i].lock
){-.-.-.}
, at: [<ffffffff81515689>] debug_check_no_obj_freed+0xd9/0x260

stack backtrace:
CPU: 0 PID: 2430 Comm: trinity-c4 Not tainted 4.11.0-rc3-think+ #3
Call Trace:
dump_stack+0x68/0x93
print_circular_bug+0x1be/0x210
__lock_acquire+0x1134/0x12b0
lock_acquire+0x102/0x260
? down_trylock+0x14/0x40
_raw_spin_lock_irqsave+0x4c/0x90
? down_trylock+0x14/0x40
? vprintk_emit+0x2ac/0x390
down_trylock+0x14/0x40
__down_trylock_console_sem+0x2f/0xa0
console_trylock+0x16/0x90
? trace_hardirqs_off+0xd/0x10
vprintk_emit+0x2ac/0x390
? debug_print_object+0x87/0xb0
vprintk_default+0x29/0x50
vprintk_func+0x25/0x80
? unwind_next_frame+0x93/0x240
printk+0x52/0x6e
? debug_print_object+0x87/0xb0
__warn+0x39/0xf0
warn_slowpath_fmt+0x5f/0x80
? debug_check_no_obj_freed+0xd9/0x260
debug_print_object+0x87/0xb0
? work_on_cpu+0xd0/0xd0
debug_check_no_obj_freed+0x219/0x260
? __sk_destruct+0x10d/0x1c0
kmem_cache_free+0x9f/0x370
__sk_destruct+0x10d/0x1c0
sk_destruct+0x20/0x30
__sk_free+0x43/0xa0
sk_free+0x18/0x20
smc_release+0x100/0x1a0 [smc]
sock_release+0x1f/0x80
sock_close+0x12/0x20
__fput+0xf3/0x200
____fput+0xe/0x10
task_work_run+0x85/0xb0
do_exit+0x331/0xd70
__secure_computing+0x9c/0xa0
syscall_trace_enter+0xd1/0x3d0
do_syscall_64+0x15f/0x1d0
entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x7f535f4b19e7
RSP: 002b:00007fff1a0f40e8 EFLAGS: 00000246
ORIG_RAX: 0000000000000008
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f535f4b19e7
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 0000000000000000 R08: 00007f535fb8b000 R09: 00c17c2740a303e4
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff1a0f40f5
R13: 00007f535fb60048 R14: 00007f535fb83ad8 R15: 00007f535fb60000

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