INFO: task hung in bcm_release

syzbot
2020-01-07T16:03:12Z

Hello,

syzbot found the following crash on:

HEAD commit: bed72351 Merge tag 'kbuild-fixes-v5.5-2' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16eeba56e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=874bac2ff63646fa
dashboard link: https://syzkaller.appspot.com/bug?extid=9d1d68a21e17513cb654
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9d1d68a21e17513cb654@syzkaller.appspotmail.com

INFO: task syz-executor.5:25823 blocked for more than 143 seconds.
Not tainted 5.5.0-rc4-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D26440 25823 10371 0x80004006
Call Trace:
context_switch kernel/sched/core.c:3385 [inline]
__schedule+0x934/0x1f90 kernel/sched/core.c:4081
schedule+0xdc/0x2b0 kernel/sched/core.c:4155
rwsem_down_write_slowpath+0x706/0xf80 kernel/locking/rwsem.c:1238
__down_write kernel/locking/rwsem.c:1392 [inline]
down_write+0x13c/0x150 kernel/locking/rwsem.c:1535
unregister_netdevice_notifier+0x7e/0x3a0 net/core/dev.c:1772
bcm_release+0x93/0x650 net/can/bcm.c:1474
__sock_release+0xce/0x280 net/socket.c:592
sock_close+0x1e/0x30 net/socket.c:1270
__fput+0x2ff/0x890 fs/file_table.c:280
____fput+0x16/0x20 fs/file_table.c:313
task_work_run+0x145/0x1c0 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0xba9/0x2f50 kernel/exit.c:801
do_group_exit+0x135/0x360 kernel/exit.c:899
get_signal+0x47c/0x24f0 kernel/signal.c:2734
do_signal+0x87/0x1700 arch/x86/kernel/signal.c:815
exit_to_usermode_loop+0x286/0x380 arch/x86/entry/common.c:160
prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
do_syscall_64+0x676/0x790 arch/x86/entry/common.c:304
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45af49
Code: Bad RIP value.
RSP: 002b:00007f5d7155ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000029
RAX: 0000000000000004 RBX: 0000000000000003 RCX: 000000000045af49
RDX: 0000000000000002 RSI: 0000000000000002 RDI: 000000000000001d
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f5d7155f6d4
R13: 00000000004cb57f R14: 00000000004e58a8 R15: 00000000ffffffff

Showing all locks held in the system:
2 locks held by kworker/u4:0/7:
1 lock held by khungtaskd/1103:
#0: ffffffff899a5680 (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x279 kernel/locking/lockdep.c:5334
1 lock held by rsyslogd/10193:
#0: ffff8880a9a7a660 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:801
2 locks held by getty/10315:
#0: ffff8880a8966090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900017e32e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/10316:
#0: ffff8880953a1090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900018832e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/10317:
#0: ffff8880a551a090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900018132e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/10318:
#0: ffff88809f175090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900018532e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/10319:
#0: ffff888094002090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900018232e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/10320:
#0: ffff888099c20090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900018732e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/10321:
#0: ffff8880a8ab1090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900017bb2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
3 locks held by kworker/u4:7/16900:
#0: ffff8880a9a96128 ((wq_completion)netns){+.+.}, at: __write_once_size
include/linux/compiler.h:226 [inline]
#0: ffff8880a9a96128 ((wq_completion)netns){+.+.}, at: arch_atomic64_set
arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff8880a9a96128 ((wq_completion)netns){+.+.}, at: atomic64_set
include/asm-generic/atomic-instrumented.h:855 [inline]
#0: ffff8880a9a96128 ((wq_completion)netns){+.+.}, at: atomic_long_set
include/asm-generic/atomic-long.h:40 [inline]
#0: ffff8880a9a96128 ((wq_completion)netns){+.+.}, at: set_work_data
kernel/workqueue.c:615 [inline]
#0: ffff8880a9a96128 ((wq_completion)netns){+.+.}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:642 [inline]
#0: ffff8880a9a96128 ((wq_completion)netns){+.+.}, at:
process_one_work+0x88b/0x1740 kernel/workqueue.c:2235
#1: ffffc90007fcfdc0 (net_cleanup_work){+.+.}, at:
process_one_work+0x8c1/0x1740 kernel/workqueue.c:2239
#2: ffffffff8a4af948 (pernet_ops_rwsem){++++}, at: cleanup_net+0xae/0xaf0
net/core/net_namespace.c:559
2 locks held by syz-executor.5/25823:
#0: ffff888091a84700 (&sb->s_type->i_mutex_key#12){+.+.}, at: inode_lock
include/linux/fs.h:791 [inline]
#0: ffff888091a84700 (&sb->s_type->i_mutex_key#12){+.+.}, at:
__sock_release+0x89/0x280 net/socket.c:591
#1: ffffffff8a4af948 (pernet_ops_rwsem){++++}, at:
unregister_netdevice_notifier+0x7e/0x3a0 net/core/dev.c:1772
1 lock held by syz-executor.0/25891:
#0: ffffffff8a4af948 (pernet_ops_rwsem){++++}, at: copy_net_ns+0x27b/0x5a0
net/core/net_namespace.c:472

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 1103 Comm: khungtaskd Not tainted 5.5.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x197/0x210 lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x23b/0x28b lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline]
watchdog+0xb11/0x10c0 kernel/hung_task.c:289
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 7 Comm: kworker/u4:0 Not tainted 5.5.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: bat_events batadv_nc_worker
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x0/0x20 kernel/kcov.c:273
Code: f6 fe ff ff 5d c3 0f 1f 40 00 55 0f b7 d6 0f b7 f7 bf 03 00 00 00 48
89 e5 48 8b 4d 08 e8 d8 fe ff ff 5d c3 66 0f 1f 44 00 00 <55> 89 f2 89 fe
bf 05 00 00 00 48 89 e5 48 8b 4d 08 e8 ba fe ff ff
RSP: 0018:ffffc90000cdfcd8 EFLAGS: 00000246
RAX: 0000000000000001 RBX: ffff8880a89978c0 RCX: 1ffffffff14f3a12
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90000cdfd30 R08: ffff8880a99f61c0 R09: ffffed1015d0703d
R10: ffffed1015d0703c R11: ffff8880ae8381e3 R12: 0000000000000001
R13: 0000000000000140 R14: 0000000000000001 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 0000000087fff000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
process_one_work+0x9af/0x1740 kernel/workqueue.c:2264
worker_thread+0x98/0xe40 kernel/workqueue.c:2410
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

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