Filtering USB storage data in kernel module

Filtering USB storage data in kernel module

[Abhijit Pawar]

Hi All,
I need to filter  the data written/read to and from the USB storage 
disk. Now the way USB is made known to OS is through SCSI and then 
respective filesystem ( mostly usbfs).
So is there any way I can intercept this stack and have my kernel module 
invoked so that I will get the data.

I have been thinking on two approaches:

1. Use VFS and write a proxy filesystem for USB device which will filter 
the data.
2. checking SCSI and any intercepting point.

I am currently looking at USBMONITOR source code as well.  Please let me 
know if there is any other way to achieve this.

Regards,
Abhijit Pawar

Filtering USB storage data in kernel module

[Greg KH]

On Thu, Nov 17, 2011 at 02:15:35PM +0530, Abhijit Pawar wrote:
> Hi All,
> I need to filter  the data written/read to and from the USB storage 
> disk.

Why?

What are you wanting to do at "filter" time?

Why just USB disks?  What makes them special?

How are you going to determine if a disk is a USB device or not?

> Now the way USB is made known to OS is through SCSI and then 
> respective filesystem ( mostly usbfs).

Not really, usbfs is only one way, and it has nothing to do with usb
disks.

> So is there any way I can intercept this stack and have my kernel module 
> invoked so that I will get the data.

Not easily.

> I have been thinking on two approaches:
> 
> 1. Use VFS and write a proxy filesystem for USB device which will filter 
> the data.
> 2. checking SCSI and any intercepting point.

Again, what are you trying to "filter"?  That will determine where you
make changes.

thanks,

greg k-h

Filtering USB storage data in kernel module

[Abhijit Pawar]

On 11/17/2011 08:19 PM, Greg KH wrote:
> On Thu, Nov 17, 2011 at 02:15:35PM +0530, Abhijit Pawar wrote:
>> Hi All,
>> I need to filter  the data written/read to and from the USB storage
>> disk.
> Why?
I want to build a secure machine with data protection. I want to have a 
security around the machine where anyone can attach a usb disk and copy 
the data. but i want to make the copied data useless unless it has the 
trust relation with the host to which its connected.
So if one has copied data from one secured machine and get that usb disk 
to other machine, he should see the encrypted garbage data.
>
> What are you wanting to do at "filter" time?
I want to encrypt the write data packets and decrypt the read data packets.
> Why just USB disks?  What makes them special?
They are the one which can be attached to the system easily.
> How are you going to determine if a disk is a USB device or not?
>
>> Now the way USB is made known to OS is through SCSI and then
>> respective filesystem ( mostly usbfs).
> Not really, usbfs is only one way, and it has nothing to do with usb
> disks.
>
>> So is there any way I can intercept this stack and have my kernel module
>> invoked so that I will get the data.
> Not easily.
Even if its hard, can you please give  details of how do I achieve this?
>> I have been thinking on two approaches:
>>
>> 1. Use VFS and write a proxy filesystem for USB device which will filter
>> the data.
>> 2. checking SCSI and any intercepting point.
> Again, what are you trying to "filter"?  That will determine where you
> make changes.
thanks, greg k-h
So what choice do I have now for this?

Filtering USB storage data in kernel module

[Greg KH]

On Fri, Nov 18, 2011 at 06:36:18PM +0530, Abhijit Pawar wrote:
> On 11/17/2011 08:19 PM, Greg KH wrote:
> >On Thu, Nov 17, 2011 at 02:15:35PM +0530, Abhijit Pawar wrote:
> >>Hi All,
> >>I need to filter  the data written/read to and from the USB storage
> >>disk.
> >Why?
> I want to build a secure machine with data protection. I want to
> have a security around the machine where anyone can attach a usb
> disk and copy the data. but i want to make the copied data useless
> unless it has the trust relation with the host to which its
> connected.
> So if one has copied data from one secured machine and get that usb
> disk to other machine, he should see the encrypted garbage data.

Interesting idea.

> >What are you wanting to do at "filter" time?
> I want to encrypt the write data packets and decrypt the read data packets.
> >Why just USB disks?  What makes them special?
> They are the one which can be attached to the system easily.
> >How are you going to determine if a disk is a USB device or not?

You forgot to answer this question :)

> >>Now the way USB is made known to OS is through SCSI and then
> >>respective filesystem ( mostly usbfs).
> >Not really, usbfs is only one way, and it has nothing to do with usb
> >disks.
> >
> >>So is there any way I can intercept this stack and have my kernel module
> >>invoked so that I will get the data.
> >Not easily.
> Even if its hard, can you please give  details of how do I achieve this?
> >>I have been thinking on two approaches:
> >>
> >>1. Use VFS and write a proxy filesystem for USB device which will filter
> >>the data.
> >>2. checking SCSI and any intercepting point.
> >Again, what are you trying to "filter"?  That will determine where you
> >make changes.
> thanks, greg k-h
> So what choice do I have now for this?

Lots of work, best of luck with this task, it will not be simple or
easy.

greg k-h

Filtering USB storage data in kernel module

[Abhijit Pawar]

On 11/18/2011 08:16 PM, Greg KH wrote:
> On Fri, Nov 18, 2011 at 06:36:18PM +0530, Abhijit Pawar wrote:
>> On 11/17/2011 08:19 PM, Greg KH wrote:
>>> On Thu, Nov 17, 2011 at 02:15:35PM +0530, Abhijit Pawar wrote:
>>>> Hi All,
>>>> I need to filter  the data written/read to and from the USB storage
>>>> disk.
>>> Why?
>> I want to build a secure machine with data protection. I want to
>> have a security around the machine where anyone can attach a usb
>> disk and copy the data. but i want to make the copied data useless
>> unless it has the trust relation with the host to which its
>> connected.
>> So if one has copied data from one secured machine and get that usb
>> disk to other machine, he should see the encrypted garbage data.
> Interesting idea.
>
>>> What are you wanting to do at "filter" time?
>> I want to encrypt the write data packets and decrypt the read data packets.
>>> Why just USB disks?  What makes them special?
>> They are the one which can be attached to the system easily.
>>> How are you going to determine if a disk is a USB device or not?
> You forgot to answer this question :)
Yeah, I forgot that one. I am not very sure but if I can patch the USB 
core before it attaches the speficied class driver to the USB device. 
May be I can try and send some control request and get the class of the 
device.  I think its not required as USB core itself will understand the 
class of the device and try to attach the proper driver. At this point 
of time, I will have some patch which will pass on the information to my 
module.
I am not sure if there are any intercepting points or any functions / 
structures exported in the USB core stack.
>
>>>> Now the way USB is made known to OS is through SCSI and then
>>>> respective filesystem ( mostly usbfs).
>>> Not really, usbfs is only one way, and it has nothing to do with usb
>>> disks.
>>>
>>>> So is there any way I can intercept this stack and have my kernel module
>>>> invoked so that I will get the data.
>>> Not easily.
>> Even if its hard, can you please give  details of how do I achieve this?
>>>> I have been thinking on two approaches:
>>>>
>>>> 1. Use VFS and write a proxy filesystem for USB device which will filter
>>>> the data.
>>>> 2. checking SCSI and any intercepting point.
>>> Again, what are you trying to "filter"?  That will determine where you
>>> make changes.
>> thanks, greg k-h
>> So what choice do I have now for this?
> Lots of work, best of luck with this task, it will not be simple or
> easy.
>
> greg k-h
Thanks. Its not that simple. I need to check the sCSI family code as 
well as USB core. Also VFS may be involved. :(  :)

Regards,
Abhijit Pawar

Filtering USB storage data in kernel module

[Abhijit Pawar]

On 11/18/2011 09:05 PM, Abhijit Pawar wrote:
> On 11/18/2011 08:16 PM, Greg KH wrote:
>> On Fri, Nov 18, 2011 at 06:36:18PM +0530, Abhijit Pawar wrote:
>>> On 11/17/2011 08:19 PM, Greg KH wrote:
>>>> On Thu, Nov 17, 2011 at 02:15:35PM +0530, Abhijit Pawar wrote:
>>>>> Hi All,
>>>>> I need to filter  the data written/read to and from the USB storage
>>>>> disk.
>>>> Why?
>>> I want to build a secure machine with data protection. I want to
>>> have a security around the machine where anyone can attach a usb
>>> disk and copy the data. but i want to make the copied data useless
>>> unless it has the trust relation with the host to which its
>>> connected.
>>> So if one has copied data from one secured machine and get that usb
>>> disk to other machine, he should see the encrypted garbage data.
>> Interesting idea.
>>
>>>> What are you wanting to do at "filter" time?
>>> I want to encrypt the write data packets and decrypt the read data 
>>> packets.
>>>> Why just USB disks?  What makes them special?
>>> They are the one which can be attached to the system easily.
>>>> How are you going to determine if a disk is a USB device or not?
>> You forgot to answer this question :)
> Yeah, I forgot that one. I am not very sure but if I can patch the USB 
> core before it attaches the speficied class driver to the USB device. 
> May be I can try and send some control request and get the class of 
> the device.  I think its not required as USB core itself will 
> understand the class of the device and try to attach the proper 
> driver. At this point of time, I will have some patch which will pass 
> on the information to my module.
> I am not sure if there are any intercepting points or any functions / 
> structures exported in the USB core stack.

It seems that the Linux notification chain should give me information 
whenever a USB device is added. I need to register for a notification 
callback in my module.

I have written a small module for this which uses the usb_register_notify()

Here is the debug trace from kernel when I add my logitech mouse to the 
system. I get the device added notification.


[30540.541134] usb 2-1.3: New USB device found, idVendor=046d, 
idProduct=c018
[30540.541143] usb 2-1.3: New USB device strings: Mfr=1, Product=2, 
SerialNumber=0
[30540.541150] usb 2-1.3: Product: USB Optical Mouse
[30540.541155] usb 2-1.3: Manufacturer: Logitech
[30540.541162] device: '2-1.3': device_add
[30540.541172] kobject: '2-1.3' (ffff8800252b0898): 
kobject_add_internal: parent: '2-1', set: 'devices'
[30540.549243] bus: 'usb': add device 2-1.3
[30540.549324] PM: Adding info for usb:2-1.3
[30540.549372] kobject: '2-1.3' (ffff8800252b0898): kobject_uevent_env
[30540.549384] kobject: '2-1.3' (ffff8800252b0898): fill_kobj_path: path 
= '/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3'
[30540.549473] bus: 'usb': driver_probe_device: matched device 2-1.3 
with driver usb
[30540.549482] bus: 'usb': really_probe: probing driver usb with device 
2-1.3
[30540.549512] usb 2-1.3: rpm_resume flags 0x4
[30540.549518] usb 2-1.3: rpm_resume returns 1
[30540.550214] device: '2-1.3:1.0': device_add
[30540.550232] kobject: '2-1.3:1.0' (ffff880100648040): 
kobject_add_internal: parent: '2-1.3', set: 'devices'
[30540.550553] bus: 'usb': add device 2-1.3:1.0
[30540.550643] PM: Adding info for usb:2-1.3:1.0
[30540.550661] kobject: '2-1.3:1.0' (ffff880100648040): kobject_uevent_env
[30540.550678] kobject: '2-1.3:1.0' (ffff880100648040): fill_kobj_path: 
path = '/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0'
[30540.550905] bus: 'usb': driver_probe_device: matched device 2-1.3:1.0 
with driver usbserial_generic
[30540.550923] bus: 'usb': really_probe: probing driver 
usbserial_generic with device 2-1.3:1.0
[30540.551178] usb 2-1.3: rpm_resume flags 0x4
[30540.551189] usb 2-1.3: rpm_resume returns 1
[30540.551458] bus: 'usb': driver_probe_device: matched device 2-1.3:1.0 
with driver usbhid
[30540.551473] bus: 'usb': really_probe: probing driver usbhid with 
device 2-1.3:1.0
[30540.551513] usb 2-1.3: rpm_resume flags 0x4
[30540.551523] usb 2-1.3: rpm_resume returns 1
[30540.552922] device: '0003:046D:C018.0002': device_add
[30540.552939] kobject: '0003:046D:C018.0002' (ffff88012b5b9898): 
kobject_add_internal: parent: '2-1.3:1.0', set: 'devices'
[30540.552981] bus: 'hid': add device 0003:046D:C018.0002
[30540.553143] PM: Adding info for hid:0003:046D:C018.0002
[30540.553159] kobject: '0003:046D:C018.0002' (ffff88012b5b9898): 
kobject_uevent_env
[30540.553176] kobject: '0003:046D:C018.0002' (ffff88012b5b9898): 
fill_kobj_path: path = 
'/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/0003:046D:C018.0002'
[30540.553352] bus: 'hid': driver_probe_device: matched device 
0003:046D:C018.0002 with driver generic-usb
[30540.553369] bus: 'hid': really_probe: probing driver generic-usb with 
device 0003:046D:C018.0002
[30540.555608] device: 'input17': device_add
[30540.555628] kobject: 'input' (ffff8800619af5a0): 
kobject_add_internal: parent: '2-1.3:1.0', set: '(null)'
[30540.555677] kobject: 'input17' (ffff8800252b5b58): 
kobject_add_internal: parent: 'input', set: 'devices'
[30540.555879] PM: Adding info for No Bus:input17
[30540.555888] kobject: 'input17' (ffff8800252b5b58): kobject_uevent_env
[30540.555899] kobject: 'input17' (ffff8800252b5b58): fill_kobj_path: 
path = 
'/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input17'
[30540.556072] kobject: 'input17' (ffff8800252b5b58): fill_kobj_path: 
path = 
'/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input17'
[30540.556087] input: Logitech USB Optical Mouse as 
/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input17
[30540.556140] device: 'mouse0': device_add
[30540.556153] kobject: 'mouse0' (ffff8800252b41b8): 
kobject_add_internal: parent: 'input17', set: 'devices'
[30540.556907] PM: Adding info for No Bus:mouse0
[30540.556924] kobject: 'mouse0' (ffff8800252b41b8): kobject_uevent_env
[30540.556940] kobject: 'mouse0' (ffff8800252b41b8): fill_kobj_path: 
path = 
'/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input17/mouse0'
[30540.557125] device: 'event6': device_add
[30540.557139] kobject: 'event6' (ffff8800252b21c0): 
kobject_add_internal: parent: 'input17', set: 'devices'
[30540.558939] PM: Adding info for No Bus:event6
[30540.558953] kobject: 'event6' (ffff8800252b21c0): kobject_uevent_env
[30540.558969] kobject: 'event6' (ffff8800252b21c0): fill_kobj_path: 
path = 
'/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input17/event6'
[30540.559198] device: 'hidraw0': device_add
[30540.559221] kobject: 'hidraw' (ffff8800619afa20): 
kobject_add_internal: parent: '0003:046D:C018.0002', set: '(null)'
[30540.559252] kobject: 'hidraw0' (ffff88012bfbc810): 
kobject_add_internal: parent: 'hidraw', set: 'devices'
[30540.559281] usbhid 2-1.3:1.0: rpm_resume flags 0x4
[30540.559293] usbhid 2-1.3:1.0: rpm_resume returns 1
[30540.559655] PM: Adding info for No Bus:hidraw0
[30540.559670] kobject: 'hidraw0' (ffff88012bfbc810): kobject_uevent_env
[30540.559687] kobject: 'hidraw0' (ffff88012bfbc810): fill_kobj_path: 
path = 
'/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/0003:046D:C018.0002/hidraw/hidraw0'
[30540.559805] generic-usb 0003:046D:C018.0002: input,hidraw0: USB HID 
v1.11 Mouse [Logitech USB Optical Mouse] on usb-0000:00:1d.0-1.3/input0
[30540.559820] driver: '0003:046D:C018.0002': driver_bound: bound to 
device 'generic-usb'
[30540.559833] bus: 'hid': really_probe: bound device 
0003:046D:C018.0002 to driver generic-usb
[30540.559859] driver: '2-1.3:1.0': driver_bound: bound to device 'usbhid'
[30540.559874] bus: 'usb': really_probe: bound device 2-1.3:1.0 to 
driver usbhid
[30540.559892] usbhid 2-1.3:1.0: rpm_suspend flags 0x4
[30540.559908] usbhid 2-1.3:1.0: rpm_suspend returns 0
[30540.559939] device: 'ep_81': device_add
[30540.559950] kobject: 'ep_81' (ffff88009613f820): 
kobject_add_internal: parent: '2-1.3:1.0', set: 'devices'
[30540.560175] PM: Adding info for No Bus:ep_81
[30540.560189] kobject: 'ep_81' (ffff88009613f820): kobject_uevent_env
[30540.560198] kobject: 'ep_81' (ffff88009613f820): kobject_uevent_env: 
filter function caused the event to drop!
[30540.561372] usb_notify_subscriber
[30540.561378] usb_notify_subscriber:USB device added


So this notification is raised when everything is done by the USB core 
and it has already attached the driver to the device. In that case I 
think this is not that important and will not solve the purpose which I 
am looking for.


>>
>>>>> Now the way USB is made known to OS is through SCSI and then
>>>>> respective filesystem ( mostly usbfs).
>>>> Not really, usbfs is only one way, and it has nothing to do with usb
>>>> disks.
>>>>
>>>>> So is there any way I can intercept this stack and have my kernel 
>>>>> module
>>>>> invoked so that I will get the data.
>>>> Not easily.
>>> Even if its hard, can you please give  details of how do I achieve 
>>> this?
>>>>> I have been thinking on two approaches:
>>>>>
>>>>> 1. Use VFS and write a proxy filesystem for USB device which will 
>>>>> filter
>>>>> the data.
>>>>> 2. checking SCSI and any intercepting point.
>>>> Again, what are you trying to "filter"?  That will determine where you
>>>> make changes.
>>> thanks, greg k-h
>>> So what choice do I have now for this?
>> Lots of work, best of luck with this task, it will not be simple or
>> easy.
>>
>> greg k-h
> Thanks. Its not that simple. I need to check the sCSI family code as 
> well as USB core. Also VFS may be involved. :(  :)
>
> Regards,
> Abhijit Pawar

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Filtering USB storage data in kernel module

[Abhijit Pawar]

On 11/21/2011 07:25 PM, Abhijit Pawar wrote:
> On 11/18/2011 09:05 PM, Abhijit Pawar wrote:
>> On 11/18/2011 08:16 PM, Greg KH wrote:
>>> On Fri, Nov 18, 2011 at 06:36:18PM +0530, Abhijit Pawar wrote:
>>>> On 11/17/2011 08:19 PM, Greg KH wrote:
>>>>> On Thu, Nov 17, 2011 at 02:15:35PM +0530, Abhijit Pawar wrote:
>>>>>> Hi All,
>>>>>> I need to filter  the data written/read to and from the USB storage
>>>>>> disk.
>>>>> Why?
>>>> I want to build a secure machine with data protection. I want to
>>>> have a security around the machine where anyone can attach a usb
>>>> disk and copy the data. but i want to make the copied data useless
>>>> unless it has the trust relation with the host to which its
>>>> connected.
>>>> So if one has copied data from one secured machine and get that usb
>>>> disk to other machine, he should see the encrypted garbage data.
>>> Interesting idea.
>>>
>>>>> What are you wanting to do at "filter" time?
>>>> I want to encrypt the write data packets and decrypt the read data 
>>>> packets.
>>>>> Why just USB disks?  What makes them special?
>>>> They are the one which can be attached to the system easily.
>>>>> How are you going to determine if a disk is a USB device or not?
>>> You forgot to answer this question :)
>> Yeah, I forgot that one. I am not very sure but if I can patch the 
>> USB core before it attaches the speficied class driver to the USB 
>> device. May be I can try and send some control request and get the 
>> class of the device.  I think its not required as USB core itself 
>> will understand the class of the device and try to attach the proper 
>> driver. At this point of time, I will have some patch which will pass 
>> on the information to my module.
>> I am not sure if there are any intercepting points or any functions / 
>> structures exported in the USB core stack.
>
> It seems that the Linux notification chain should give me information 
> whenever a USB device is added. I need to register for a notification 
> callback in my module.
>
> I have written a small module for this which uses the 
> usb_register_notify()
>
> Here is the debug trace from kernel when I add my logitech mouse to 
> the system. I get the device added notification.
>
>
> [30540.541134] usb 2-1.3: New USB device found, idVendor=046d, 
> idProduct=c018
> [30540.541143] usb 2-1.3: New USB device strings: Mfr=1, Product=2, 
> SerialNumber=0
> [30540.541150] usb 2-1.3: Product: USB Optical Mouse
> [30540.541155] usb 2-1.3: Manufacturer: Logitech
> [30540.541162] device: '2-1.3': device_add
> [30540.541172] kobject: '2-1.3' (ffff8800252b0898): 
> kobject_add_internal: parent: '2-1', set: 'devices'
> [30540.549243] bus: 'usb': add device 2-1.3
> [30540.549324] PM: Adding info for usb:2-1.3
> [30540.549372] kobject: '2-1.3' (ffff8800252b0898): kobject_uevent_env
> [30540.549384] kobject: '2-1.3' (ffff8800252b0898): fill_kobj_path: 
> path = '/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3'
> [30540.549473] bus: 'usb': driver_probe_device: matched device 2-1.3 
> with driver usb
> [30540.549482] bus: 'usb': really_probe: probing driver usb with 
> device 2-1.3
> [30540.549512] usb 2-1.3: rpm_resume flags 0x4
> [30540.549518] usb 2-1.3: rpm_resume returns 1
> [30540.550214] device: '2-1.3:1.0': device_add
> [30540.550232] kobject: '2-1.3:1.0' (ffff880100648040): 
> kobject_add_internal: parent: '2-1.3', set: 'devices'
> [30540.550553] bus: 'usb': add device 2-1.3:1.0
> [30540.550643] PM: Adding info for usb:2-1.3:1.0
> [30540.550661] kobject: '2-1.3:1.0' (ffff880100648040): kobject_uevent_env
> [30540.550678] kobject: '2-1.3:1.0' (ffff880100648040): 
> fill_kobj_path: path = 
> '/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0'
> [30540.550905] bus: 'usb': driver_probe_device: matched device 
> 2-1.3:1.0 with driver usbserial_generic
> [30540.550923] bus: 'usb': really_probe: probing driver 
> usbserial_generic with device 2-1.3:1.0
> [30540.551178] usb 2-1.3: rpm_resume flags 0x4
> [30540.551189] usb 2-1.3: rpm_resume returns 1
> [30540.551458] bus: 'usb': driver_probe_device: matched device 
> 2-1.3:1.0 with driver usbhid
> [30540.551473] bus: 'usb': really_probe: probing driver usbhid with 
> device 2-1.3:1.0
> [30540.551513] usb 2-1.3: rpm_resume flags 0x4
> [30540.551523] usb 2-1.3: rpm_resume returns 1
> [30540.552922] device: '0003:046D:C018.0002': device_add
> [30540.552939] kobject: '0003:046D:C018.0002' (ffff88012b5b9898): 
> kobject_add_internal: parent: '2-1.3:1.0', set: 'devices'
> [30540.552981] bus: 'hid': add device 0003:046D:C018.0002
> [30540.553143] PM: Adding info for hid:0003:046D:C018.0002
> [30540.553159] kobject: '0003:046D:C018.0002' (ffff88012b5b9898): 
> kobject_uevent_env
> [30540.553176] kobject: '0003:046D:C018.0002' (ffff88012b5b9898): 
> fill_kobj_path: path = 
> '/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/0003:046D:C018.0002'
> [30540.553352] bus: 'hid': driver_probe_device: matched device 
> 0003:046D:C018.0002 with driver generic-usb
> [30540.553369] bus: 'hid': really_probe: probing driver generic-usb 
> with device 0003:046D:C018.0002
> [30540.555608] device: 'input17': device_add
> [30540.555628] kobject: 'input' (ffff8800619af5a0): 
> kobject_add_internal: parent: '2-1.3:1.0', set: '(null)'
> [30540.555677] kobject: 'input17' (ffff8800252b5b58): 
> kobject_add_internal: parent: 'input', set: 'devices'
> [30540.555879] PM: Adding info for No Bus:input17
> [30540.555888] kobject: 'input17' (ffff8800252b5b58): kobject_uevent_env
> [30540.555899] kobject: 'input17' (ffff8800252b5b58): fill_kobj_path: 
> path = 
> '/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input17'
> [30540.556072] kobject: 'input17' (ffff8800252b5b58): fill_kobj_path: 
> path = 
> '/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input17'
> [30540.556087] input: Logitech USB Optical Mouse as 
> /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input17
> [30540.556140] device: 'mouse0': device_add
> [30540.556153] kobject: 'mouse0' (ffff8800252b41b8): 
> kobject_add_internal: parent: 'input17', set: 'devices'
> [30540.556907] PM: Adding info for No Bus:mouse0
> [30540.556924] kobject: 'mouse0' (ffff8800252b41b8): kobject_uevent_env
> [30540.556940] kobject: 'mouse0' (ffff8800252b41b8): fill_kobj_path: 
> path = 
> '/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input17/mouse0'
> [30540.557125] device: 'event6': device_add
> [30540.557139] kobject: 'event6' (ffff8800252b21c0): 
> kobject_add_internal: parent: 'input17', set: 'devices'
> [30540.558939] PM: Adding info for No Bus:event6
> [30540.558953] kobject: 'event6' (ffff8800252b21c0): kobject_uevent_env
> [30540.558969] kobject: 'event6' (ffff8800252b21c0): fill_kobj_path: 
> path = 
> '/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input17/event6'
> [30540.559198] device: 'hidraw0': device_add
> [30540.559221] kobject: 'hidraw' (ffff8800619afa20): 
> kobject_add_internal: parent: '0003:046D:C018.0002', set: '(null)'
> [30540.559252] kobject: 'hidraw0' (ffff88012bfbc810): 
> kobject_add_internal: parent: 'hidraw', set: 'devices'
> [30540.559281] usbhid 2-1.3:1.0: rpm_resume flags 0x4
> [30540.559293] usbhid 2-1.3:1.0: rpm_resume returns 1
> [30540.559655] PM: Adding info for No Bus:hidraw0
> [30540.559670] kobject: 'hidraw0' (ffff88012bfbc810): kobject_uevent_env
> [30540.559687] kobject: 'hidraw0' (ffff88012bfbc810): fill_kobj_path: 
> path = 
> '/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/0003:046D:C018.0002/hidraw/hidraw0'
> [30540.559805] generic-usb 0003:046D:C018.0002: input,hidraw0: USB HID 
> v1.11 Mouse [Logitech USB Optical Mouse] on usb-0000:00:1d.0-1.3/input0
> [30540.559820] driver: '0003:046D:C018.0002': driver_bound: bound to 
> device 'generic-usb'
> [30540.559833] bus: 'hid': really_probe: bound device 
> 0003:046D:C018.0002 to driver generic-usb
> [30540.559859] driver: '2-1.3:1.0': driver_bound: bound to device 'usbhid'
> [30540.559874] bus: 'usb': really_probe: bound device 2-1.3:1.0 to 
> driver usbhid
> [30540.559892] usbhid 2-1.3:1.0: rpm_suspend flags 0x4
> [30540.559908] usbhid 2-1.3:1.0: rpm_suspend returns 0
> [30540.559939] device: 'ep_81': device_add
> [30540.559950] kobject: 'ep_81' (ffff88009613f820): 
> kobject_add_internal: parent: '2-1.3:1.0', set: 'devices'
> [30540.560175] PM: Adding info for No Bus:ep_81
> [30540.560189] kobject: 'ep_81' (ffff88009613f820): kobject_uevent_env
> [30540.560198] kobject: 'ep_81' (ffff88009613f820): 
> kobject_uevent_env: filter function caused the event to drop!
> [30540.561372] usb_notify_subscriber
> [30540.561378] usb_notify_subscriber:USB device added
>
>
> So this notification is raised when everything is done by the USB core 
> and it has already attached the driver to the device. In that case I 
> think this is not that important and will not solve the purpose which 
> I am looking for.
>
>
>>>
>>>>>> Now the way USB is made known to OS is through SCSI and then
>>>>>> respective filesystem ( mostly usbfs).
>>>>> Not really, usbfs is only one way, and it has nothing to do with usb
>>>>> disks.
>>>>>
>>>>>> So is there any way I can intercept this stack and have my kernel 
>>>>>> module
>>>>>> invoked so that I will get the data.
>>>>> Not easily.
>>>> Even if its hard, can you please give  details of how do I achieve 
>>>> this?
>>>>>> I have been thinking on two approaches:
>>>>>>
>>>>>> 1. Use VFS and write a proxy filesystem for USB device which will 
>>>>>> filter
>>>>>> the data.
>>>>>> 2. checking SCSI and any intercepting point.
>>>>> Again, what are you trying to "filter"?  That will determine where 
>>>>> you
>>>>> make changes.
>>>> thanks, greg k-h
>>>> So what choice do I have now for this?
>>> Lots of work, best of luck with this task, it will not be simple or
>>> easy.
>>>
>>> greg k-h
>> Thanks. Its not that simple. I need to check the sCSI family code as 
>> well as USB core. Also VFS may be involved. :(  :)
>>
>> Regards,
>> Abhijit Pawar
>
Hi ,
I found a rather very simple solution to the problem. Stackable filesystem.

Regards,
Abhijit Pawar
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