linux-kernel - [PATCH v2 1/1] usb: musb: gadget: misplaced out of bounds check

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Message-Id: <20180320022735.4548-1-xypron.glpk@gmx.de>
Date:   Tue, 20 Mar 2018 03:27:35 +0100
From:   Heinrich Schuchardt <xypron.glpk@....de>
To:     Bin Liu <b-liu@...com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Heinrich Schuchardt <xypron.glpk@....de>
Subject: [PATCH v2 1/1] usb: musb: gadget: misplaced out of bounds check

musb->endpoints[] has array size MUSB_C_NUM_EPS.
We must check array bounds before accessing the array and not afterwards.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
---
v2
	Only the 4 low bits of epnum are relevant for indexing.	
---
 drivers/usb/musb/musb_gadget_ep0.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/musb/musb_gadget_ep0.c b/drivers/usb/musb/musb_gadget_ep0.c
index 18da4873e52e..96b0fa12f729 100644
--- a/drivers/usb/musb/musb_gadget_ep0.c
+++ b/drivers/usb/musb/musb_gadget_ep0.c
@@ -89,15 +89,20 @@ static int service_tx_status_request(
 		}
 
 		is_in = epnum & USB_DIR_IN;
+		epnum &= 0x0f;
+		if (epnum >= MUSB_C_NUM_EPS) {
+			handled = -EINVAL;
+			break;
+		}
+
 		if (is_in) {
-			epnum &= 0x0f;
 			ep = &musb->endpoints[epnum].ep_in;
 		} else {
 			ep = &musb->endpoints[epnum].ep_out;
 		}
 		regs = musb->endpoints[epnum].regs;
 
-		if (epnum >= MUSB_C_NUM_EPS || !ep->desc) {
+		if (!ep->desc) {
 			handled = -EINVAL;
 			break;
 		}
-- 
2.16.2