linux-kernel - [PATCH] usb: gadget: prevent potenial null pointer dereference on skb->len

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Message-Id: <20160905153712.15205-1-colin.king@canonical.com>
Date:   Mon,  5 Sep 2016 16:37:12 +0100
From:   Colin King <colin.king@...onical.com>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Chen <peter.chen@....com>,
        Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
        Nicholas Bellinger <nab@...ux-iscsi.org>,
        Robert Baldyga <r.baldyga@...sung.com>,
        John Youn <John.Youn@...opsys.com>, linux-usb@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] usb: gadget: prevent potenial null pointer dereference on skb->len

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

An earlier fix partially fixed the null pointer dereference on skb->len
by moving the assignment of len after the check on skb being non-null,
however it failed to remove the erroneous dereference when assigning len.
Correctly fix this by removing the initialisation of len as was
originally intended.

Fixes: 70237dc8efd092 ("usb: gadget: function: f_eem: socket buffer may be NULL")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/usb/gadget/function/f_eem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/f_eem.c b/drivers/usb/gadget/function/f_eem.c
index 8741fd7..007ec6e 100644
--- a/drivers/usb/gadget/function/f_eem.c
+++ b/drivers/usb/gadget/function/f_eem.c
@@ -342,7 +342,7 @@ static struct sk_buff *eem_wrap(struct gether *port, struct sk_buff *skb)
 	struct sk_buff	*skb2 = NULL;
 	struct usb_ep	*in = port->in_ep;
 	int		headroom, tailroom, padlen = 0;
-	u16		len = skb->len;
+	u16		len;
 
 	if (!skb)
 		return NULL;
-- 
2.9.3