Subject: INFO: task hung in cancel_delayed_work_sync

From: syzbot <[email-masked]>
Date: Mon, 16 Sep 2019 03:19:06 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    f4b752a6 mlx4: fix spelling mistake "veify" -> "verify"
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=1183c7fa600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b89bb446a3faaba4
dashboard link: https://syzkaller.appspot.com/bug?extid=f39ab8494f6015e62360
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14426d85600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=110c1af1600000

The bug was bisected to:

commit 3c4d7559159bfe1e3b94df3a657b2cda3a34e218
Author: Dave Watson <[email-masked]>
Date:   Wed Jun 14 18:37:39 2017 +0000

     tls: kernel TLS support

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=144a4ffa600000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=164a4ffa600000
console output: https://syzkaller.appspot.com/x/log.txt?x=124a4ffa600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]
Fixes: 3c4d7559159b ("tls: kernel TLS support")

INFO: task syz-executor279:9995 blocked for more than 143 seconds.
       Not tainted 5.3.0-rc7+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor279 D24264  9995   9994 0x00000000
Call Trace:
  context_switch kernel/sched/core.c:3254 [inline]
  __schedule+0x755/0x1580 kernel/sched/core.c:3880
  schedule+0xd9/0x260 kernel/sched/core.c:3947
  schedule_timeout+0x717/0xc50 kernel/time/timer.c:1783
  do_wait_for_common kernel/sched/completion.c:83 [inline]
  __wait_for_common kernel/sched/completion.c:104 [inline]
  wait_for_common kernel/sched/completion.c:115 [inline]
  wait_for_completion+0x29c/0x440 kernel/sched/completion.c:136
  __flush_work+0x508/0xa50 kernel/workqueue.c:3040
  __cancel_work_timer+0x3d9/0x540 kernel/workqueue.c:3127
  cancel_delayed_work_sync+0x1b/0x20 kernel/workqueue.c:3259
  tls_sw_cancel_work_tx+0x68/0x80 net/tls/tls_sw.c:2063
  tls_sk_proto_close+0x4ac/0x990 net/tls/tls_main.c:299
  inet_release+0xed/0x200 net/ipv4/af_inet.c:427
  inet6_release+0x53/0x80 net/ipv6/af_inet6.c:470
  __sock_release+0xce/0x280 net/socket.c:590
  sock_close+0x1e/0x30 net/socket.c:1268
  __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
  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
  exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:163
  prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
  do_syscall_64+0x5a9/0x6a0 arch/x86/entry/common.c:299
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x401f40
Code: ff ff ff 25 62 63 20 00 68 08 00 00 00 e9 60 ff ff ff ff 25 5a 63 20  
00 68 09 00 00 00 e9 50 ff ff ff ff 25 52 63 20 00 68 0a <00> 00 00 e9 40  
ff ff ff ff 25 4a 63 20 00 68 0b 00 00 00 e9 30 ff
RSP: 002b:00007fffd8200d58 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000401f40
RDX: ffffffffffffffc1 RSI: 1201000000003618 RDI: 0000000000000004
RBP: 00007fffd8200d70 R08: 0000000000000000 R09: 1201000000003618
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000403170 R14: 0000000000000000 R15: 0000000000000000
INFO: lockdep is turned off.
NMI backtrace for cpu 1
CPU: 1 PID: 1057 Comm: khungtaskd Not tainted 5.3.0-rc7+ #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+0x172/0x1f0 lib/dump_stack.c:113
  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+0x9d0/0xef0 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 skipped: idling at native_safe_halt+0xe/0x10  
arch/x86/include/asm/irqflags.h:60

---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email-masked].

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches