Am Mittwoch, 27. Januar 2021, 09:50:34 CET schrieb Heiko Stuebner:

From: Heiko Stuebner <redacted>

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 <redacted>
Cc: stable@vger.kernel.org

superseeded by v3, which includes an appropriate Reported-by tag