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

[Mathias Nyman]

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