[RESEND] xhci: Use xhci_get_virt_ep() to validate ep_index

ring_doorbell_for_active_rings() API is being called from
multiple context. This specific API tries to get virt_dev
based endpoint using passed slot_id and ep_index. Some caller
API is having check against slot_id and ep_index using
xhci_get_virt_ep() API whereas xhci_handle_cmd_config_ep() API
only check ep_index against -1 value but not upper bound i.e.
EP_CTX_PER_DEV. Hence use xhci_get_virt_ep() API to get virt_dev
based endpoint which checks both slot_id and ep_index to get
valid endpoint.

Signed-off-by: Mayank Rana <quic_mrana@quicinc.com>
---
 drivers/usb/host/xhci-ring.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

On Fri, Apr 29, 2022 at 12:49:59PM +0300, Mathias Nyman wrote:
> On 28.4.2022 22.04, Mayank Rana wrote:
> > ring_doorbell_for_active_rings() API is being called from
> > multiple context. This specific API tries to get virt_dev
> > based endpoint using passed slot_id and ep_index. Some caller
> > API is having check against slot_id and ep_index using
> > xhci_get_virt_ep() API whereas xhci_handle_cmd_config_ep() API
> > only check ep_index against -1 value but not upper bound i.e.
> > EP_CTX_PER_DEV. Hence use xhci_get_virt_ep() API to get virt_dev
> > based endpoint which checks both slot_id and ep_index to get
> > valid endpoint.
> 
> ep_index upper bound is known to be in range as EP_CTX_PER_DEV is 31,
> and ep_index = fls(u32 value)  - 1 - 1; 
> 
> We can change to use xhci_get_virt_ep(), but this would be more useful
> earlier in xhci_handle_cmd_config_ep() where we touch the ep before
> calling ring_doorbell_for_active_rings()
> 
> Also note that this codepath is only used for some prototype
> xHC controller that probably never made it to the market about 10 years ago.

Can we just delete the codepath entirely then?

thanks,

greg k-h

On Fri, Apr 29, 2022 at 01:23:50PM +0300, Mathias Nyman wrote:
> On 29.4.2022 13.02, Greg KH wrote:
> > On Fri, Apr 29, 2022 at 12:49:59PM +0300, Mathias Nyman wrote:
> >> On 28.4.2022 22.04, Mayank Rana wrote:
> >>> ring_doorbell_for_active_rings() API is being called from
> >>> multiple context. This specific API tries to get virt_dev
> >>> based endpoint using passed slot_id and ep_index. Some caller
> >>> API is having check against slot_id and ep_index using
> >>> xhci_get_virt_ep() API whereas xhci_handle_cmd_config_ep() API
> >>> only check ep_index against -1 value but not upper bound i.e.
> >>> EP_CTX_PER_DEV. Hence use xhci_get_virt_ep() API to get virt_dev
> >>> based endpoint which checks both slot_id and ep_index to get
> >>> valid endpoint.
> >>
> >> ep_index upper bound is known to be in range as EP_CTX_PER_DEV is 31,
> >> and ep_index = fls(u32 value)  - 1 - 1; 
> >>
> >> We can change to use xhci_get_virt_ep(), but this would be more useful
> >> earlier in xhci_handle_cmd_config_ep() where we touch the ep before
> >> calling ring_doorbell_for_active_rings()
> >>
> >> Also note that this codepath is only used for some prototype
> >> xHC controller that probably never made it to the market about 10 years ago.
> > 
> > Can we just delete the codepath entirely then?
> 
> Probably.
> Commit ac9d8fe7c6a8 USB: xhci: Add quirk for Fresco Logic xHCI hardware.
> that added this states:
> 
> "This patch is for prototype hardware that will be given to other companies
> for evaluation purposes only, and should not reach consumer hands.  Fresco
> Logic's next chip rev should have this bug fixed."
> 
> Should we print some warning instead if this controller is used?
> just in case. 

Would be a good idea, see if that hardware did actually get out into the
wild.

thanks,

greg k-h

On 29.4.2022 22.01, Mayank Rana wrote:
> On 4/29/2022 3:13 AM, Mathias Nyman wrote:
>> On 29.4.2022 12.49, Mathias Nyman wrote:
>>> On 28.4.2022 22.04, Mayank Rana wrote:
>>>> ring_doorbell_for_active_rings() API is being called from
>>>> multiple context. This specific API tries to get virt_dev
>>>> based endpoint using passed slot_id and ep_index. Some caller
>>>> API is having check against slot_id and ep_index using
>>>> xhci_get_virt_ep() API whereas xhci_handle_cmd_config_ep() API
>>>> only check ep_index against -1 value but not upper bound i.e.
>>>> EP_CTX_PER_DEV. Hence use xhci_get_virt_ep() API to get virt_dev
>>>> based endpoint which checks both slot_id and ep_index to get
>>>> valid endpoint.
>>> ep_index upper bound is known to be in range as EP_CTX_PER_DEV is 31,
>>> and ep_index = fls(u32 value)  - 1 - 1;
>>>
>>> We can change to use xhci_get_virt_ep(), but this would be more useful
>>> earlier in xhci_handle_cmd_config_ep() where we touch the ep before
>>> calling ring_doorbell_for_active_rings()
>>>
>> After a second look I would appreciate if you could clean up
>> ep_index checking in xhci_handle_cmd_config_ep()
>>
>> It currenty does some horrible typecasting.
>> ep_index is an unsigned int, so the fls() -1 operation might wrap it around.
>> Checking this was solved by typecasting a -1 to an unsigned int.
>>
>> if (ep_index != (unsigned int) -1)
>>
>> Thanks
>> Mathias
> 
> Thanks Mathias for review and suggestion here.
> let me try to clean up xhci_handle_cmd_config_ep() API based ep_index usage.
> 

Please don't spend too much time on this,
I'm going to remove this code as Greg suggested.

Should have replied earlier, sorry about the delay

Thanks
-Mathias