usb/gadget: potential deadlock in gadgetfs_suspend

[Andrey Konovalov]

Hi,

I'm getting some hangs while fuzzing the kernel with syzkaller.

Possibly it happens during the execution of the following syzkaller program:

mmap(&(0x7f0000000000/0xb90000)=nil, (0xb90000), 0x3, 0x32,
0xffffffffffffffff, 0x0)
r0 = open$usb(&(0x7f0000001000)="2f6465762f6761646765742f64756d6d795f75646300",
0xc002, 0x0)
r1 = open$usb(&(0x7f0000002000)="2f6465762f6761646765742f64756d6d795f75646300",
0x1, 0x102)
write$usb(r1, &(0x7f0000003000)={0x0, {0x9, 0x2, 0x1b, 0x0, 0x5, 0x0,
0x80, 0x8, 0x9, 0x4, 0x10000000, 0xfffffefffffffff9, 0x1, 0xff, 0x0,
0x8, 0x80, [{0x9, 0x5, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}]}, {0x12, 0x1,
0x0, 0x0, 0x4b5, 0x7c, 0x0, 0x3, 0x4, 0x0, 0x8, 0xd686, 0x0, 0x1}},
0x31)

I haven't managed to get the exact same stack trace (or any at all
actually) while trying to reproduce the bug with this program, but the
kernel definitely hangs.

On commit b29794ec95c6856b316c2295904208bf11ffddd9 (4.12-rc4+) with
Alan's patch applied.

gadgetfs: bound to dummy_udc driver
gadgetfs: suspended from state 2
INFO: rcu_sched detected stalls on CPUs/tasks:
1-...: (0 ticks this GP) idle=966/140000000000000/0 softirq=37706/37706 fqs=5250
(detected by 2, t=21002 jiffies, g=26575, c=26574, q=183)
Sending NMI from CPU 2 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 1394 Comm: kworker/1:2 Not tainted 4.12.0-rc4+ #24
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: usb_hub_wq hub_event
task: ffff88003ebfb640 task.stack: ffffc900024fc000
RIP: 0010:rep_nop arch/x86/include/asm/processor.h:619 [inline]
RIP: 0010:cpu_relax arch/x86/include/asm/processor.h:624 [inline]
RIP: 0010:virt_spin_lock arch/x86/include/asm/qspinlock.h:63 [inline]
RIP: 0010:queued_spin_lock_slowpath+0x20/0x1a0 kernel/locking/qspinlock.c:421
RSP: 0018:ffffc900024ff9f0 EFLAGS: 00000002
RAX: 000000007d72e420 RBX: ffff88007d72e768 RCX: 0000000000010000
RDX: 0000000000000001 RSI: 000000007d72e420 RDI: ffff88007d72e768
RBP: ffffc900024ff9f0 R08: 0000000000000006 R09: 0000000000000020
R10: ffffc900024ffa50 R11: 0000000000d52301 R12: ffff88007da9c298
R13: 0000000000000000 R14: 0000000000000000 R15: ffffffff82cfc5a0
FS:  0000000000000000(0000) GS:ffff88003ed00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f728a487000 CR3: 00000000371e6000 CR4: 00000000000006e0
Call Trace:
 __raw_spin_lock include/asm-generic/qspinlock.h:103 [inline]
 _raw_spin_lock+0x1c/0x20 kernel/locking/spinlock.c:151
 spin_lock include/linux/spinlock.h:299 [inline]
 gadgetfs_suspend+0x32/0x90 drivers/usb/gadget/legacy/inode.c:1684
 set_link_state+0x39c/0x440 drivers/usb/gadget/udc/dummy_hcd.c:455
 dummy_hub_control+0x3e7/0x650 drivers/usb/gadget/udc/dummy_hcd.c:2074
 rh_call_control drivers/usb/core/hcd.c:689 [inline]
 rh_urb_enqueue drivers/usb/core/hcd.c:846 [inline]
 usb_hcd_submit_urb+0x327/0xcf0 drivers/usb/core/hcd.c:1650
 usb_submit_urb+0x355/0x6f0 drivers/usb/core/urb.c:542
 usb_start_wait_urb+0x5f/0x110 drivers/usb/core/message.c:56
 usb_internal_control_msg drivers/usb/core/message.c:100 [inline]
 usb_control_msg+0xd9/0x120 drivers/usb/core/message.c:151
 usb_clear_port_feature+0x46/0x60 drivers/usb/core/hub.c:412
 hub_port_disable+0x65/0x1d0 drivers/usb/core/hub.c:4177
 hub_port_init+0x10a/0xee0 drivers/usb/core/hub.c:4648
 hub_port_connect drivers/usb/core/hub.c:4826 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:4999 [inline]
 port_event drivers/usb/core/hub.c:5105 [inline]
 hub_event+0xa0b/0x16e0 drivers/usb/core/hub.c:5189
 process_one_work+0x1fb/0x4c0 kernel/workqueue.c:2097
 process_scheduled_works kernel/workqueue.c:2157 [inline]
 worker_thread+0x2ab/0x4c0 kernel/workqueue.c:2233
 kthread+0x140/0x160 kernel/kthread.c:231
 ret_from_fork+0x25/0x30 arch/x86/entry/entry_64.S:424
Code: 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 0f 1f 44 00 00 ba
01 00 00 00 8b 07 85 c0 75 0a f0 0f b1 17 85 c0 75 f2 5d c3 f3 90 <eb>
ec 81 fe 00 01 00 00 0f 84 92 00 00 00 41 b8 01 01 00 00 b9