From f670e9f9c8cac716c3506c6bac9e997b27ad441a Mon Sep 17 00:00:00 2001
From: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Date: Wed, 27 Jan 2021 11:39:19 +0100
Subject: [PATCH] usb: dwc2: Fix endpoint direction check in ep_from_windex
Git-commit: f670e9f9c8cac716c3506c6bac9e997b27ad441a
Patch-mainline: v5.11-rc7
References: git-fixes

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/usb/dwc2/gadget.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
index 0a0d11151cfb..ad4c94366dad 100644
--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -1543,7 +1543,6 @@ static void dwc2_hsotg_complete_oursetup(struct usb_ep *ep,
 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;
 
@@ -1553,12 +1552,7 @@ 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);
 }
 
 /**
-- 
2.26.2