[PATCH 4.9 27/43] usb: dwc2: Fix endpoint direction check in ep_from_windex

Greg Kroah-Hartman
2021-02-08T15:51:51Z

From: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>

commit f670e9f9c8cac716c3506c6bac9e997b27ad441a upstream.

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")
Cc: stable@vger.kernel.org
Reported-by: Gerhard Klostermeier <gerhard.klostermeier@syss.de>
Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Link: https://lore.kernel.org/r/20210127103919.58215-1-heiko@sntech.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/dwc2/gadget.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)

--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -942,7 +942,6 @@ static void dwc2_hsotg_complete_oursetup
static struct dwc2_hsotg_ep *ep_from_windex(struct dwc2_hsotg *hsotg,
u32 windex)
{
- struct dwc2_hsotg_ep *ep;
int dir = (windex & USB_DIR_IN) ? 1 : 0;
int idx = windex & 0x7F;

@@ -952,12 +951,7 @@ static struct dwc2_hsotg_ep *ep_from_win
if (idx > hsotg->num_of_eps)
return NULL;

- ep = index_to_ep(hsotg, idx, dir);
-
- if (idx && ep->dir_in != dir)
- return NULL;
-
- return ep;
+ return index_to_ep(hsotg, idx, dir);
}

/**