linux-kernel - Re: usb/gadget: potential deadlock in gadgetfs

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Message-ID: <CAAeHK+xVTvcPh5ynKfOs-MryvsCkJ0M1Y=BV2echV6fM99EBDg@mail.gmail.com>
Date:   Fri, 9 Jun 2017 15:08:44 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Chen <peter.chen@....com>,
        Krzysztof Opasiak <k.opasiak@...sung.com>,
        Colin Ian King <colin.king@...onical.com>,
        Felix Hädicke <felixhaedicke@....de>,
        Roger Quadros <rogerq@...com>,
        USB list <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alan Stern <stern@...land.harvard.edu>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: usb/gadget: potential deadlock in gadgetfs_suspend

On Fri, Jun 9, 2017 at 2:41 PM, Andrey Konovalov <andreyknvl@...gle.com> wrote:
> 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.

Never mind, this program is unrelated to the hang.

>
> 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