Hi,

Andrey Konovalov <andreyknvl@google.com> writes:
> Hi!
>
> I've got the following error report while running the syzkaller fuzzer.
>
> On commit 3c49de52d5647cda8b42c4255cf8a29d1e22eff5 (Dec 2).
>
> WARNING: CPU: 0 PID: 5257 at drivers/usb/gadget/udc/dummy_hcd.c:672
> dummy_free_request+0x153/0x170
> Kernel panic - not syncing: panic_on_warn set ...
>
> usb 2-1: string descriptor 0 read error: -71
> usb 2-1: New USB device found, idVendor=0000, idProduct=0000
> usb 2-1: New USB device strings: Mfr=0, Product=170, SerialNumber=0
> CPU: 0 PID: 5257 Comm: syz-executor0 Not tainted 4.9.0-rc7+ #16
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>  ffff88006af0ec48 ffffffff81f96aba ffffffff00000200 1ffff1000d5e1d1c
>  ffffed000d5e1d14 0000000000000a06 0000000041b58ab3 ffffffff8598b4c8
>  ffffffff81f96828 0000000041b58ab3 ffffffff85942a10 ffffffff81432790
> Call Trace:
>  [<     inline     >] __dump_stack lib/dump_stack.c:15
>  [<ffffffff81f96aba>] dump_stack+0x292/0x398 lib/dump_stack.c:51
>  [<ffffffff8168c7be>] panic+0x1cb/0x3a9 kernel/panic.c:179
>  [<ffffffff812b80b4>] __warn+0x1c4/0x1e0 kernel/panic.c:542
>  [<ffffffff812b831c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
>  [<ffffffff830fcac3>] dummy_free_request+0x153/0x170
> drivers/usb/gadget/udc/dummy_hcd.c:672
>  [<ffffffff830ed160>] usb_ep_free_request+0xc0/0x420
> drivers/usb/gadget/udc/core.c:195
>  [<ffffffff83224fe1>] gadgetfs_unbind+0x131/0x190
> drivers/usb/gadget/legacy/inode.c:1612
>  [<ffffffff830ebcbf>] usb_gadget_remove_driver+0x10f/0x2b0
> drivers/usb/gadget/udc/core.c:1228
>  [<ffffffff830ec016>] usb_gadget_unregister_driver+0x1b6/0x2c0
> drivers/usb/gadget/udc/core.c:1357
>  [<ffffffff83224650>] dev_release+0x80/0x160
> drivers/usb/gadget/legacy/inode.c:1187
>  [<ffffffff81805852>] __fput+0x332/0x7f0 fs/file_table.c:208
>  [<ffffffff81805d95>] ____fput+0x15/0x20 fs/file_table.c:244
>  [<ffffffff81338b9b>] task_work_run+0x19b/0x270 kernel/task_work.c:116
>  [<     inline     >] exit_task_work include/linux/task_work.h:21
>  [<ffffffff812c7eca>] do_exit+0x16aa/0x2530 kernel/exit.c:828
>  [<ffffffff812cd749>] do_group_exit+0x149/0x420 kernel/exit.c:932
>  [<ffffffff812faa9d>] get_signal+0x76d/0x17b0 kernel/signal.c:2307
>  [<ffffffff811cfee2>] do_signal+0xd2/0x2120 arch/x86/kernel/signal.c:807
>  [<ffffffff81003d00>] exit_to_usermode_loop+0x170/0x200
> arch/x86/entry/common.c:156
>  [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:190
>  [<ffffffff81007293>] syscall_return_slowpath+0x3d3/0x420
> arch/x86/entry/common.c:259
>  [<ffffffff84f47f62>] entry_SYSCALL_64_fastpath+0xc0/0xc2
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled

There have been several emails like this one. Can you check if
my branch testing/fixes is working for you?

-- 
balbi