Re: [PATCH] usb: dwc2: Fix endpoint direction check in ep_from_windex

[Heiko Stübner]

Am Montag, 25. Januar 2021, 20:13:24 CET schrieb Heiko Stuebner:
> From: Heiko Stuebner <heiko.stuebner@xxxxxxxxxxxxxxxxxxxxx>
> 
> dwc2_hsotg_process_req_status uses ep_from_windex() to retrieve
> the endpoint for the index provided in the wIndex request param.
> 
> In a test-case with a rndis gadget running and sending a malformed
> packet to it like:
>     dev.ctrl_transfer(
>         0x82,      # bmRequestType
>         0x00,       # bRequest
>         0x0000,     # wValue
>         0x0001,     # wIndex
>         0x00       # wLength
>     )
> it is possible to cause a crash:
> 
> [  217.533022] dwc2 ff300000.usb: dwc2_hsotg_process_req_status: USB_REQ_GET_STATUS
> [  217.559003] Unable to handle kernel read from unreadable memory at virtual address 0000000000000088
> ...
> [  218.313189] Call trace:
> [  218.330217]  ep_from_windex+0x3c/0x54
> [  218.348565]  usb_gadget_giveback_request+0x10/0x20
> [  218.368056]  dwc2_hsotg_complete_request+0x144/0x184
> 
> This happens because ep_from_windex wants to compare the endpoint
> direction even if index_to_ep() didn't return an endpoint due to
> the direction not matching.
> 
> The fix is easy insofar that the actual direction check is already
> happening when calling index_to_ep() which will return NULL if there
> is no endpoint for the targeted direction, so the offending check
> can go away completely.
> 
> Fixes: c6f5c050e2a7 ("usb: dwc2: gadget: add bi-directional endpoint support")
> Signed-off-by: Heiko Stuebner <heiko.stuebner@xxxxxxxxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

superseeded by v3, which includes an appropriate Reported-by tag
and removes an now unused variable (in v2).