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

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

[Heiko Stuebner]

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

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@theobroma-systems.com>
Cc: stable@vger.kernel.org
---
 drivers/usb/dwc2/gadget.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
index 70ac47a341ac..a68c01b1dd73 100644
--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -1553,12 +1553,7 @@ static struct dwc2_hsotg_ep *ep_from_windex(struct dwc2_hsotg *hsotg,
 	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);
 }
 
 /**
-- 
2.29.2

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@theobroma-systems.com>
> 
> 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@theobroma-systems.com>
> Cc: stable@vger.kernel.org

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