BUG: bpf: task hung in tcx_link_release

[Kenneth Lee]

Hi,

The following hung task was found by a custom fuzzer developed
by Sechang Lim <rhkrqnwk98@xxxxxxxxx>:

  INFO: task syz.0.604:4415 blocked for more than 123 seconds.

Unfortunately, we haven't found a reproducer for the hang yet. We'll
inform you if we have any update on the hang.

Detailed crash information is attached below.

Thanks,
Kenneth Lee

---
- Kernel version:
7.1.0-rc6

- Crash Report:
INFO: task syz.0.604:4415 blocked for more than 123 seconds.
      Not tainted 7.1.0-rc6-dirty #34
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.604       state:D stack:27816 pid:4415  tgid:4415  ppid:2655   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5388 [inline]
 __schedule+0x1f31/0x2e80 kernel/sched/core.c:7189
 __schedule_loop kernel/sched/core.c:7268 [inline]
 schedule+0x167/0x360 kernel/sched/core.c:7283
 schedule_preempt_disabled+0x15/0x30 kernel/sched/core.c:7340
 __mutex_lock_common kernel/locking/mutex.c:726 [inline]
 __mutex_lock+0x60a/0x1380 kernel/locking/mutex.c:820
 tcx_link_release+0x6e/0x4b0 kernel/bpf/tcx.c:177
 bpf_link_free+0xec/0x4a0 kernel/bpf/syscall.c:3273
 bpf_link_put_direct kernel/bpf/syscall.c:3326 [inline]
 bpf_link_release+0x7d/0x90 kernel/bpf/syscall.c:3333
 __fput+0x454/0xa70 fs/file_table.c:510
 task_work_run+0x197/0x210 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
 exit_to_user_mode_loop+0x10f/0x550 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x306/0x480 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x551c0d
RSP: 002b:00007ffec2926448 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00000000007d7da0 RCX: 0000000000551c0d
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000007d7da0 R08: 0000000000000009 R09: 0000000000000001
R10: 00000000003fd15c R11: 0000000000000246 R12: 000000000002e6bb
R13: ffffffffffffffff R14: 00000000007d5fa0 R15: 00000000007d5fac
 </TASK>
INFO: task syz.0.604:4415 is blocked on a mutex likely owned by task kworker/u8:42:1561.
task:kworker/u8:42   state:R  running task     stack:27016 pid:1561  tgid:1561  ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: netns cleanup_net