usb/gadget: another GPF in usb_gadget_unregister_driver

[Andrey Konovalov]

Hi,

I've got the following error report while fuzzing the kernel with syzkaller.

On commit b29794ec95c6856b316c2295904208bf11ffddd9 (4.12-rc4+).

This looks quite similar to
https://groups.google.com/forum/#!topic/syzkaller/HDawLBeeORI

I'm able to reproduce this, so I can collect some debug traces if needed.

kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 2 PID: 4820 Comm: syz-executor0 Not tainted 4.12.0-rc4+ #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff880039542dc0 task.stack: ffff88003bdd0000
RIP: 0010:__list_del_entry_valid+0x7e/0x170 lib/list_debug.c:51
RSP: 0018:ffff88003bdd6e50 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000010000
RDX: 0000000000000000 RSI: ffffffff86504948 RDI: ffffffff86504950
RBP: ffff88003bdd6e68 R08: ffff880039542dc0 R09: ffffffff8778ce00
R10: ffff88003bdd6e68 R11: dffffc0000000000 R12: 0000000000000000
R13: dffffc0000000000 R14: 1ffff100077badd2 R15: ffffffff864d2e40
FS:  0000000000000000(0000) GS:ffff88006dc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002014aff9 CR3: 0000000006022000 CR4: 00000000000006e0
Call Trace:
 __list_del_entry include/linux/list.h:116 [inline]
 list_del include/linux/list.h:124 [inline]
 usb_gadget_unregister_driver+0x166/0x4c0 drivers/usb/gadget/udc/core.c:1387
 dev_release+0x80/0x160 drivers/usb/gadget/legacy/inode.c:1187
 __fput+0x332/0x7f0 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:245
 task_work_run+0x19b/0x270 kernel/task_work.c:116
 exit_task_work include/linux/task_work.h:21 [inline]
 do_exit+0x18a3/0x2820 kernel/exit.c:878
 do_group_exit+0x149/0x420 kernel/exit.c:982
 get_signal+0x77f/0x1780 kernel/signal.c:2318
 do_signal+0xd2/0x2130 arch/x86/kernel/signal.c:808
 exit_to_usermode_loop+0x1a7/0x240 arch/x86/entry/common.c:157
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath+0x3ba/0x410 arch/x86/entry/common.c:263
 entry_SYSCALL_64_fastpath+0xbc/0xbe
RIP: 0033:0x4461f9
RSP: 002b:00007fdac2b1ecf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00000000007080c8 RCX: 00000000004461f9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000007080c8
RBP: 00000000007080a8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fdac2b1f9c0 R15: 00007fdac2b1f700
Code: 00 00 00 00 ad de 49 39 c4 74 6a 48 b8 00 02 00 00 00 00 ad de
48 89 da 48 39 c3 74 74 48 c1 ea 03 48 b8 00 00 00 00 00 fc ff df <80>
3c 02 00 0f 85 92 00 00 00 48 8b 13 48 39 f2 75 66 49 8d 7c
RIP: __list_del_entry_valid+0x7e/0x170 lib/list_debug.c:51 RSP: ffff88003bdd6e50
---[ end trace 30e94b1eec4831c8 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..