usb/gadget: warning in dummy_free_request

[Andrey Konovalov]

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