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

[Mathias Nyman]

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. 

Thanks
Mathias