[PATCH v4 0/2] Fix syzkaller bug: hung task in hub_port_init

[Anirudh Rayabharam]

This series fixes the hung task bug in hub_port_init reported by
syzkaller at:

https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76

Stack:

INFO: task kworker/0:0:5 blocked for more than 143 seconds.
      Not tainted 5.13.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:0     state:D
 stack:27392 pid:    5 ppid:     2 flags:0x00004000
Workqueue: usb_hub_wq hub_event

Call Trace:
 context_switch kernel/sched/core.c:4339 [inline]
 __schedule+0x916/0x23e0 kernel/sched/core.c:5147
 schedule+0xcf/0x270 kernel/sched/core.c:5226
 usb_kill_urb.part.0+0x19c/0x220 drivers/usb/core/urb.c:711
 usb_kill_urb+0x81/0xa0 drivers/usb/core/urb.c:706
 usb_start_wait_urb+0x24a/0x4c0 drivers/usb/core/message.c:64
 usb_internal_control_msg drivers/usb/core/message.c:102 [inline]
 usb_control_msg+0x31c/0x4a0 drivers/usb/core/message.c:153
 hub_port_init+0x82e/0x2db0 drivers/usb/core/hub.c:4759
 hub_port_connect drivers/usb/core/hub.c:5210 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5418 [inline]
 port_event drivers/usb/core/hub.c:5564 [inline]
 hub_event+0x2190/0x4330 drivers/usb/core/hub.c:5646
 process_one_work+0x98d/0x1600 kernel/workqueue.c:2276
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2422
 kthread+0x3b1/0x4a0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The first patch in the series fixes the issue and the second patch does
some refactoring to avoid duplicate code.

Changes in v4:
- Got rid of the log messages as suggested by Shuah.

Changes in v3:
- Split the patch into two patches
- Remove the convenience wrappers as suggested by Shuah
- Remove the WARN as suggested by Greg
Link: https://lore.kernel.org/lkml/20210813182508.28127-1-mail@xxxxxxxxxxxxx/

Changes in v2:
Use WARN_ON() instead of BUG() when unlink_list is neither unlink_tx nor
unlink_rx.
Link: https://lore.kernel.org/lkml/20210806181335.2078-1-mail@xxxxxxxxxxxxx/

v1: https://lore.kernel.org/lkml/20210806164015.25263-1-mail@xxxxxxxxxxxxx/

Anirudh Rayabharam (2):
  usbip: give back URBs for unsent unlink requests during cleanup
  usbip: clean up code in vhci_device_unlink_cleanup

 drivers/usb/usbip/vhci_hcd.c | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

-- 
2.26.2