linux-kernel - [PATCH 3.18 23/36] usb: gadget: dont dereference g until after it has been null checked

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Message-Id: <20180205182352.725948225@linuxfoundation.org>
Date:   Mon,  5 Feb 2018 10:23:51 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Colin Ian King <colin.king@...onical.com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 3.18 23/36] usb: gadget: dont dereference g until after it has been null checked

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Colin Ian King <colin.king@...onical.com>


[ Upstream commit b2fc059fa549fe6881d4c1f8d698b0f50bcd16ec ]

Avoid dereferencing pointer g until after g has been sanity null checked;
move the assignment of cdev much later when it is required into a more
local scope.

Detected by CoverityScan, CID#1222135 ("Dereference before null check")

Fixes: b785ea7ce662 ("usb: gadget: composite: fix ep->maxburst initialization")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/usb/gadget/composite.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -103,7 +103,6 @@ int config_ep_by_speed(struct usb_gadget
 			struct usb_function *f,
 			struct usb_ep *_ep)
 {
-	struct usb_composite_dev	*cdev = get_gadget_data(g);
 	struct usb_endpoint_descriptor *chosen_desc = NULL;
 	struct usb_descriptor_header **speed_desc = NULL;
 
@@ -170,8 +169,12 @@ ep_found:
 			_ep->maxburst = comp_desc->bMaxBurst + 1;
 			break;
 		default:
-			if (comp_desc->bMaxBurst != 0)
+			if (comp_desc->bMaxBurst != 0) {
+				struct usb_composite_dev *cdev;
+
+				cdev = get_gadget_data(g);
 				ERROR(cdev, "ep0 bMaxBurst must be 0\n");
+			}
 			_ep->maxburst = 1;
 			break;
 		}