INFO: task hung in dvb_usb_i2c_exit on v7.3-rc2

[CJ]

Hi,


I am reporting a hung task in dvb_usb_i2c_exit. It is still reproducible on
Linux v7.3-rc2 (HEAD df2908090cda368b01ff43709f51890076c56157) with a syzkaller reproducer.
syzbot originally reported "INFO: task hung in dvb_usb_i2c_exit" on linux-6.1
(https://syzkaller.appspot.com/bug?extid=2e0307b121d180fca081). The target console shows a matching failure signature.


The reproducer probes and then tears down a DVB USB adapter, reaching dvb_usb_i2c_exit while the i2c adapter still has outstanding work.


On the target, the kernel reports:
  INFO: task kworker/1:1:44 blocked for more than 142 seconds.


The diagnostic path is i2c_del_adapter -> dvb_usb_i2c_exit -> dvb_usb_device_exit -> cxusb_probe.
It shares 19 key stack frames with the original hung task
report, including wait_for_completion, i2c_del_adapter, dvb_usb_i2c_exit, dvb_usb_device_exit.


This looks like the i2c adapter teardown waiting for a completion that the emulated device never signals.


This is a follow-up for an existing syzbot report and describes an
observed failure, not a bisected root cause.


Reproducer:
  syz reproducer:

syz_open_dev$usbfs(&(0x7f00000000c0), 0x203, 0x8401)
syz_usb_connect(0x0, 0x24, &(0x7f0000000380)=ANY=[@ANYBLOB="120100004b41460860163209ea800102030109021e0001000000000904"], 0x0)
syz_open_dev$I2C(&(0x7f0000000000), 0x0, 0x402)
syz_open_dev$I2C(&(0x7f0000000000), 0x1, 0x402)
syz_open_dev$I2C(&(0x7f0000000000), 0x2, 0x402)
syz_open_dev$I2C(&(0x7f0000000000), 0x3, 0x402)
syz_open_dev$I2C(&(0x7f0000000000), 0x4, 0x402)
syz_open_dev$I2C(&(0x7f0000000000), 0x5, 0x402)
syz_open_dev$I2C(&(0x7f0000000000), 0x6, 0x402)
syz_open_dev$I2C(&(0x7f0000000000), 0x7, 0x402)
bpf$MAP_CREATE(0x0, 0x0, 0x50)
sendmsg$nl_route_sched(0xffffffffffffffff, 0x0, 0x800)
sched_setscheduler(0x0, 0x2, 0x0)
sendmsg$nl_generic(0xffffffffffffffff, 0x0, 0xc000)
sendmsg$NFT_BATCH(0xffffffffffffffff, 0x0, 0x0)



console output: https://pastebin.com/raw/1La2BM5e
kernel config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=6a5cbd268406bf43


Kernel:
  HEAD commit: df2908090cda368b01ff43709f51890076c56157
  git tree: linux-stable
  kernel version: 7.3.0-rc2
  tested tag: v7.3-rc2


Let me know if you need more details or testing.


Thanks.