linux-kernel - [PATCH] drivers: usb: gadget: udc: Fix NULL dereference

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Date:	Tue, 3 Mar 2015 18:28:42 +0530
From:	Tapasweni Pathak <tapaswenipathak@...il.com>
To:	balbi@...com, gregkh@...uxfoundation.org, peter.chen@...escale.com,
	jg1.han@...sung.com, benoit.taine@...6.fr,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	julia.lawall@...6.fr, tapaswenipathak@...il.com
Subject: [PATCH] drivers: usb: gadget: udc: Fix NULL dereference

This patch fixes multiple instances of null pointer dereference in this code.

ep->udc is assigned to udc. ep is just an offset from _ep. _ep is then
checked for NULL. udc is dereferenced under the NULL check for _ep, making
an invalid pointer reference.

udc is then checked for NULL, if NULL, it is then dereferenced as
udc->dev.

To fix these issues, shift assignment of udc by dereferencing ep after
null check for _ep, replace both dev_dbg statements with pr_debug.

Found using Coccinelle.

Signed-off-by: Tapasweni Pathak <tapaswenipathak@...il.com>
Suggested-by : Julia Lawall <julia.lawall@...6.fr>
Reviewed-by : Julia Lawall <julia.lawall@...6.fr>
---
 drivers/usb/gadget/udc/lpc32xx_udc.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/gadget/udc/lpc32xx_udc.c b/drivers/usb/gadget/udc/lpc32xx_udc.c
index 27fd413..6398539 100644
--- a/drivers/usb/gadget/udc/lpc32xx_udc.c
+++ b/drivers/usb/gadget/udc/lpc32xx_udc.c
@@ -1807,17 +1807,16 @@ static int lpc32xx_ep_queue(struct usb_ep *_ep,
 	    !list_empty(&req->queue))
 		return -EINVAL;

-	udc = ep->udc;
-
 	if (!_ep) {
-		dev_dbg(udc->dev, "invalid ep\n");
+		pr_debug("invalid ep\n");
 		return -EINVAL;
 	}

+	udc = ep->udc;

 	if ((!udc) || (!udc->driver) ||
 	    (udc->gadget.speed == USB_SPEED_UNKNOWN)) {
-		dev_dbg(udc->dev, "invalid device\n");
+		pr_debug("invalid device\n");
 		return -EINVAL;
 	}

--
1.7.9.5

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