Re: usb/media/uvc: warning in uvc_scan_chain_forward/__list_add

[Laurent Pinchart]

Hi Andrey,

On Tuesday, 26 September 2017 15:41:45 EEST Andrey Konovalov wrote:
> On Tue, Sep 26, 2017 at 10:43 AM, Laurent Pinchart wrote:
> > On Monday, 25 September 2017 15:40:13 EEST Andrey Konovalov wrote:
> >> Hi!
> >> 
> >> I've got the following report while fuzzing the kernel with syzkaller.
> > 
> > Thank you for the report.
> > 
> >> On commit e19b205be43d11bff638cad4487008c48d21c103 (4.14-rc2).
> >> 
> >> list_add double add: new=ffff880069084010, prev=ffff880069084010,
> >> next=ffff880067d22298.
> >> ------------[ cut here ]------------
> >> WARNING: CPU: 1 PID: 1846 at lib/list_debug.c:31
> >> __list_add_valid+0xbd/0xf0
> >> Modules linked in:
> >> CPU: 1 PID: 1846 Comm: kworker/1:2 Not tainted
> >> 4.14.0-rc2-42613-g1488251d1a98 #238
> >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
> >> 01/01/2011 Workqueue: usb_hub_wq hub_event
> >> task: ffff88006b01ca40 task.stack: ffff880064358000
> >> RIP: 0010:__list_add_valid+0xbd/0xf0 lib/list_debug.c:29
> >> RSP: 0018:ffff88006435ddd0 EFLAGS: 00010286
> >> RAX: 0000000000000058 RBX: ffff880067d22298 RCX: 0000000000000000
> >> RDX: 0000000000000058 RSI: ffffffff85a58800 RDI: ffffed000c86bbac
> >> RBP: ffff88006435dde8 R08: 1ffff1000c86ba52 R09: 0000000000000000
> >> R10: 0000000000000002 R11: 0000000000000000 R12: ffff880069084010
> >> R13: ffff880067d22298 R14: ffff880069084010 R15: ffff880067d222a0
> >> FS:  0000000000000000(0000) GS:ffff88006c900000(0000)
> >> knlGS:0000000000000000 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> CR2: 0000000020004ff2 CR3: 000000006b447000 CR4: 00000000000006e0
> >> 
> >> Call Trace:
> >>  __list_add ./include/linux/list.h:59
> >>  list_add_tail+0x8c/0x1b0 ./include/linux/list.h:92
> >>  uvc_scan_chain_forward.isra.8+0x373/0x416
> >> 
> >> drivers/media/usb/uvc/uvc_driver.c:1471
> >> 
> >>  uvc_scan_chain drivers/media/usb/uvc/uvc_driver.c:1585
> >>  uvc_scan_device drivers/media/usb/uvc/uvc_driver.c:1769
> >>  uvc_probe+0x77f2/0x8f00 drivers/media/usb/uvc/uvc_driver.c:2104
> > 
> > So the issue happens at probe time, before the driver registers the V4L2
> > device nodes that allow userspace access to the device. I wonder how
> > fuzzing caused this. Do you have a more detailed log ?
> > 
> > Could you also tell me what webcam you're using to test this out ? The
> > output of lsusb -v would be useful.
> 
> Hi Laurent,
> 
> I fuzz the USB stack externally by emulating random USB devices via
> dummy_hcd and gadgetfs.

Ah that makes more sense indeed.

> lsusb -v doesn't show anything, since the USB device doesn't finish
> initialization.
> 
> Since I'm able to reproduce this, I can collect debug traces for you.

Could you send me the descriptors that your gadget driver returns to the host 
? If that's difficult, as an alternative, could you enable tracing in the 
uvcvideo driver (uvcvideo.trace=0xffff on the kernel commmand line for 
instance) and send me the kernel log ?

> Here's a part of the log around the warning report:
> 
> gadgetfs: bound to dummy_udc driver
> usb 1-1: new full-speed USB device number 2 using dummy_hcd
> gadgetfs: connected
> gadgetfs: disconnected
> gadgetfs: connected
> usb 1-1: config 3 has an invalid interface number: 3 but max is 0
> usb 1-1: config 3 contains an unexpected descriptor of type 0x1, skipping
> usb 1-1: config 3 has an invalid descriptor of length 208, skipping
> remainder of the config
> usb 1-1: config 3 has no interface number 0
> usb 1-1: New USB device found, idVendor=07f5, idProduct=03ff
> usb 1-1: New USB device strings: Mfr=83, Product=255, SerialNumber=5
> usb 1-1: Product: a
> usb 1-1: Manufacturer: a
> usb 1-1: SerialNumber: a
> gadgetfs: configuration #3
> uvcvideo: Found UVC 0.00 device a (07f5:03ff)
> list_add double add: new=ffff880069a64910, prev=ffff880069a64910,
> next=ffff8800698468d8.
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 1846 at lib/list_debug.c:31 __list_add_valid+0xbd/0xf0
> ...
> ---[ end trace ea45186b02846d5a ]---
> uvcvideo 1-1:3.3: Entity type for entity a was not initialized!
> gadgetfs: disconnected
> usb 1-1: USB disconnect, device number 2
> 
> Thanks!
> 
> >>  usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361
> >>  really_probe drivers/base/dd.c:413
> >>  driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
> >>  __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
> >>  bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
> >>  __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
> >>  device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
> >>  bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
> >>  device_add+0xd0b/0x1660 drivers/base/core.c:1835
> >>  usb_set_configuration+0x104e/0x1870 drivers/usb/core/message.c:1932
> >>  generic_probe+0x73/0xe0 drivers/usb/core/generic.c:174
> >>  usb_probe_device+0xaf/0xe0 drivers/usb/core/driver.c:266
> >>  really_probe drivers/base/dd.c:413
> >>  driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
> >>  __device_attach_driver+0x230/0x290 drivers/base/dd.c:653
> >>  bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
> >>  __device_attach+0x26e/0x3d0 drivers/base/dd.c:710
> >>  device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
> >>  bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
> >>  device_add+0xd0b/0x1660 drivers/base/core.c:1835
> >>  usb_new_device+0x7b8/0x1020 drivers/usb/core/hub.c:2457
> >>  hub_port_connect drivers/usb/core/hub.c:4903
> >>  hub_port_connect_change drivers/usb/core/hub.c:5009
> >>  port_event drivers/usb/core/hub.c:5115
> >>  hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
> >>  process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
> >>  worker_thread+0x221/0x1850 kernel/workqueue.c:2253
> >>  kthread+0x3a1/0x470 kernel/kthread.c:231
> >>  ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431
> >> 
> >> Code: f1 48 c7 c7 c0 89 a5 85 48 89 de e8 38 34 e1 fe 0f ff 31 c0 eb
> >> c3 48 89 f2 48 89 d9 4c 89 e6 48 c7 c7 40 8a a5 85 e8 1d 34 e1 fe <0f>
> >> ff 31 c0 eb a8 48 89 75 e8 e8 e4 b3 2a ff 48 8b 75 e8 e9 5b
> >> ---[ end trace 23181469b7a6915e ]---

-- 
Regards,

Laurent Pinchart