On 4/15/19 12:48 PM, Andrey Konovalov wrote: > On Fri, Apr 12, 2019 at 9:46 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >> >> Andrey: >> >> It's really hard to tell just what's going on here. >> >> On Fri, 12 Apr 2019, syzbot wrote: >> >>> Hello, >>> >>> syzbot found the following crash on: >>> >>> HEAD commit: 9a33b369 usb-fuzzer: main usb gadget fuzzer driver >>> git tree: https://github.com/google/kasan/tree/usb-fuzzer >>> console output: https://syzkaller.appspot.com/x/log.txt?x=14c4c1af200000 >>> kernel config: https://syzkaller.appspot.com/x/.config?x=23e37f59d94ddd15 >>> dashboard link: https://syzkaller.appspot.com/bug?extid=d919b0f29d7b5a4994b9 >>> compiler: gcc (GCC) 9.0.0 20181231 (experimental) >>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14410dbb200000 >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f0acd3200000 >>> >>> IMPORTANT: if you fix the bug, please add the following tag to the commit: >>> Reported-by: syzbot+d919b0f29d7b5a4994b9@xxxxxxxxxxxxxxxxxxxxxxxxx >>> >>> usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22 >>> usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22 >>> usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22 >>> usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22 >>> usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22 >>> INFO: task kworker/0:2:532 blocked for more than 143 seconds. >>> Not tainted 5.1.0-rc4-319354-g9a33b36 #3 >>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >>> kworker/0:2 D26656 532 2 0x80000000 >>> Workqueue: usb_hub_wq hub_event >>> Call Trace: >>> schedule+0x8f/0x180 kernel/sched/core.c:3562 >>> usb_kill_urb drivers/usb/core/urb.c:695 [inline] >>> usb_kill_urb+0x22a/0x2c0 drivers/usb/core/urb.c:687 >>> usb_start_wait_urb+0x257/0x4d0 drivers/usb/core/message.c:63 >>> usb_internal_control_msg drivers/usb/core/message.c:101 [inline] >>> usb_control_msg+0x321/0x4a0 drivers/usb/core/message.c:152 >> >> It looks like something is stuck waiting for usb_kill_urb() to finish. >> But what happened before that? > > This crash is somewhat special. It happens quite often during USB > fuzzing, but at the same time it's a hang, which makes it a bit harder > debug. I initially thought that is somehow related to my custom USB > fuzzing kernel patches, but then I saw that someone else hit this > issue while doing USB fuzzing in a completely different way that > doesn't require kernel modifications. So it might be an actual issue > in the kernel. > > The full console output is provided by the syzbot, but I guess it's > not very useful in this case. I've just made sure that this issue is > manually reproducible, so we can easily retest it with debug patches > (syzbot should be also able to do that via the syz test command). Or > is there a way to turn on some verbose mode to see some USB debug > messages? > >> >> I can't tell from the reproducer source, because it uses a bunch of >> special stuff you added in your usb-fuzzer tree. >> >> Alan Stern >> > > I understand, for now I guess the simpler way to debug this is to run > the reproducer. I'll write you and Greg a separate email regarding all > that special stuff that I added. > Hi Andrey, Please, CC me on that email too. Thanks -- Gustavo
