Re: [PATCH] v4l2: uvcvideo use after free bug fix

[Laurent Pinchart]

Hans,

On Tuesday 06 September 2011 14:08:08 Dave Young wrote:
> Reported-by: Sitsofe Wheeler <sitsofe@xxxxxxxxx>
> Signed-off-by: Dave Young <hidave.darkstar@xxxxxxxxx>
> Tested-by: Sitsofe Wheeler <sitsofe@xxxxxxxxx>
> Acked-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> 
> Unplugging uvc video camera trigger following oops:
> 
> eeepc kernel: [ 1393.500719] usb 3-2: USB disconnect, device number 4
> eeepc kernel: [ 1393.504351] uvcvideo: Failed to resubmit video URB (-19).
> eeepc kernel: [ 1495.428853] BUG: unable to handle kernel paging request at
> 6b6b6bcb eeepc kernel: [ 1495.429017] IP: [<b0358d37>]
> dev_get_drvdata+0x17/0x20 eeepc kernel: [ 1495.429017] *pde = 00000000
> eeepc kernel: [ 1495.429017] Oops: 0000 [#1] DEBUG_PAGEALLOC
> eeepc kernel: [ 1495.429017]
> eeepc kernel: [ 1495.429017] Pid: 3476, comm: cheese Not tainted
> 3.1.0-rc3-00270-g7a54f5e-dirty #485 ASUSTeK Computer INC. 900/900 eeepc
> kernel: [ 1495.429017] EIP: 0060:[<b0358d37>] EFLAGS: 00010202 CPU: 0
> eeepc kernel: [ 1495.429017] EIP is at dev_get_drvdata+0x17/0x20
> eeepc kernel: [ 1495.429017] EAX: 6b6b6b6b EBX: eb08d870 ECX: 00000000 EDX:
> eb08d930 eeepc kernel: [ 1495.429017] ESI: eb08d870 EDI: eb08d870 EBP:
> d3249cac ESP: d3249cac eeepc kernel: [ 1495.429017]  DS: 007b ES: 007b FS:
> 0000 GS: 00e0 SS: 0068 eeepc kernel: [ 1495.429017] Process cheese (pid:
> 3476, ti=d3248000 task=df46d870 task.ti=d3248000) eeepc kernel: [
> 1495.429017] Stack:
> eeepc kernel: [ 1495.429017]  d3249cb8 b03e77a1 d307b840 d3249ccc b03e77d1
> d307b840 eb08d870 eb08d830 eeepc kernel: [ 1495.429017]  d3249ce4 b03ed3b7
> 00000246 d307b840 eb08d870 d3021b80 d3249cec b03ed565 eeepc kernel: [
> 1495.429017]  d3249cfc b03e044d e8323d10 b06e013c d3249d18 b0355fb9
> fffffffe d3249d1c eeepc kernel: [ 1495.429017] Call Trace:
> eeepc kernel: [ 1495.429017]  [<b03e77a1>] v4l2_device_disconnect+0x11/0x30
> eeepc kernel: [ 1495.429017]  [<b03e77d1>] v4l2_device_unregister+0x11/0x50
> eeepc kernel: [ 1495.429017]  [<b03ed3b7>] uvc_delete+0x37/0x110
> eeepc kernel: [ 1495.429017]  [<b03ed565>] uvc_release+0x25/0x30
> eeepc kernel: [ 1495.429017]  [<b03e044d>] v4l2_device_release+0x9d/0xc0
> eeepc kernel: [ 1495.429017]  [<b0355fb9>] device_release+0x19/0x90
> eeepc kernel: [ 1495.429017]  [<b03adfdc>] ? usb_hcd_unlink_urb+0x7c/0x90
> eeepc kernel: [ 1495.429017]  [<b026b99c>] kobject_release+0x3c/0x90
> eeepc kernel: [ 1495.429017]  [<b026b960>] ? kobject_del+0x30/0x30
> eeepc kernel: [ 1495.429017]  [<b026ca4c>] kref_put+0x2c/0x60
> eeepc kernel: [ 1495.429017]  [<b026b88d>] kobject_put+0x1d/0x50
> eeepc kernel: [ 1495.429017]  [<b03b2385>] ?
> usb_autopm_put_interface+0x25/0x30 eeepc kernel: [ 1495.429017] 
> [<b03f0e5d>] ? uvc_v4l2_release+0x5d/0xd0 eeepc kernel: [ 1495.429017] 
> [<b0355d2f>] put_device+0xf/0x20
> eeepc kernel: [ 1495.429017]  [<b03dfa96>] v4l2_release+0x56/0x60
> eeepc kernel: [ 1495.429017]  [<b019c8dc>] fput+0xcc/0x220
> eeepc kernel: [ 1495.429017]  [<b01990f4>] filp_close+0x44/0x70
> eeepc kernel: [ 1495.429017]  [<b012b238>] put_files_struct+0x158/0x180
> eeepc kernel: [ 1495.429017]  [<b012b100>] ? put_files_struct+0x20/0x180
> eeepc kernel: [ 1495.429017]  [<b012b2a0>] exit_files+0x40/0x50
> eeepc kernel: [ 1495.429017]  [<b012b9e7>] do_exit+0x5a7/0x660
> eeepc kernel: [ 1495.429017]  [<b0135f72>] ? __dequeue_signal+0x12/0x120
> eeepc kernel: [ 1495.429017]  [<b055edf2>] ? _raw_spin_unlock_irq+0x22/0x30
> eeepc kernel: [ 1495.429017]  [<b012badc>] do_group_exit+0x3c/0xb0
> eeepc kernel: [ 1495.429017]  [<b015792b>] ? trace_hardirqs_on+0xb/0x10
> eeepc kernel: [ 1495.429017]  [<b013755f>]
> get_signal_to_deliver+0x18f/0x570 eeepc kernel: [ 1495.429017] 
> [<b01020f7>] do_signal+0x47/0x9e0
> eeepc kernel: [ 1495.429017]  [<b055edf2>] ? _raw_spin_unlock_irq+0x22/0x30
> eeepc kernel: [ 1495.429017]  [<b015792b>] ? trace_hardirqs_on+0xb/0x10
> eeepc kernel: [ 1495.429017]  [<b0123300>] ? T.1034+0x30/0xc0
> eeepc kernel: [ 1495.429017]  [<b055c45f>] ? schedule+0x29f/0x640
> eeepc kernel: [ 1495.429017]  [<b0102ac8>] do_notify_resume+0x38/0x40
> eeepc kernel: [ 1495.429017]  [<b055f154>] work_notifysig+0x9/0x11
> eeepc kernel: [ 1495.429017] Code: e5 5d 83 f8 01 19 c0 f7 d0 83 e0 f0 c3
> 8d b4 26 00 00 00 00 55 85 c0 89 e5 75 09 31 c0 5d c3 90 8d 74 26 00 8b 40
> 04 85 c0 74 f0 <8b> 40 60 5d c3 8d 74 26 00 55 89 e5 53 89 c3 83 ec 04 8b
> 40 04 eeepc kernel: [ 1495.429017] EIP: [<b0358d37>]
> dev_get_drvdata+0x17/0x20 SS:ESP 0068:d3249cac eeepc kernel: [
> 1495.429017] CR2: 000000006b6b6bcb
> eeepc kernel: [ 1495.466975] uvcvideo: Failed to resubmit video URB (-27).
> eeepc kernel: [ 1495.467860] uvcvideo: Failed to resubmit video URB (-27).
> eeepc kernel: last message repeated 3 times
> eeepc kernel: [ 1495.512610] ---[ end trace 73ec16848794e5a5 ]---
> 
> For uvc device, dev->vdev.dev is the &intf->dev,
> uvc_delete code is as below:
> 	usb_put_intf(dev->intf);
> 	usb_put_dev(dev->udev);
> 
> 	uvc_status_cleanup(dev);
> 	uvc_ctrl_cleanup_device(dev);
> 
> ## the intf dev is released above, so below code will oops.
> 
> 	if (dev->vdev.dev)
> 		v4l2_device_unregister(&dev->vdev);
> 
> Fix it by get_device in v4l2_device_register and put_device in
> v4l2_device_disconnect ---
>  drivers/media/video/v4l2-device.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/media/video/v4l2-device.c
> b/drivers/media/video/v4l2-device.c index c72856c..e6a2c3b 100644
> --- a/drivers/media/video/v4l2-device.c
> +++ b/drivers/media/video/v4l2-device.c
> @@ -38,6 +38,7 @@ int v4l2_device_register(struct device *dev, struct
> v4l2_device *v4l2_dev) mutex_init(&v4l2_dev->ioctl_lock);
>  	v4l2_prio_init(&v4l2_dev->prio);
>  	kref_init(&v4l2_dev->ref);
> +	get_device(dev);
>  	v4l2_dev->dev = dev;

We store a reference to the device in v4l2_dev, and we use it later. We thus 
need either get a reference to the device (like done by this patch), or 
mandate drivers not to release their reference to the device before calling 
v4l2_device_unregister and/or v4l2_device_disconnect (in this case that would 
mean moving the usb_put_intf call after the v4l2_device_unregister call in the 
uvcvideo driver).

Do you have a preference ?

>  	if (dev == NULL) {
>  		/* If dev == NULL, then name must be filled in by the caller */
> @@ -93,6 +94,7 @@ void v4l2_device_disconnect(struct v4l2_device *v4l2_dev)
> 
>  	if (dev_get_drvdata(v4l2_dev->dev) == v4l2_dev)
>  		dev_set_drvdata(v4l2_dev->dev, NULL);
> +	put_device(v4l2_dev->dev);
>  	v4l2_dev->dev = NULL;
>  }
>  EXPORT_SYMBOL_GPL(v4l2_device_disconnect);

-- 
Regards,

Laurent Pinchart
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