linux-kernel - [PATCH 3.16 020/254] usb: gadget: don't dereference g until after it has been null checked

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Message-ID: <lsq.1519831218.979753141@decadent.org.uk>
Date:   Wed, 28 Feb 2018 15:20:18 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Felipe Balbi" <felipe.balbi@...ux.intel.com>,
        "Colin Ian King" <colin.king@...onical.com>
Subject: [PATCH 3.16 020/254] usb: gadget: don't dereference g until after
 it has been null checked

3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

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

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

commit b2fc059fa549fe6881d4c1f8d698b0f50bcd16ec upstream.

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: Ben Hutchings <ben@...adent.org.uk>
---
 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;
 
@@ -175,8 +174,12 @@ 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;
 		}