On Mon, Apr 15, 2019 at 01:39:57PM -0500, Gustavo A. R. Silva wrote: > > > 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. Please cc: all of linux-usb@xxxxxxxxxxxxxxx, no need to keep anything private. thanks, greg k-h
