Bluetooth: Fix error code in chan_alloc_skb_cb()

[ Upstream commit 72d061ee63 ]

The chan_alloc_skb_cb() function is supposed to return error pointers on
error.  Returning NULL will lead to a NULL dereference.

Fixes: 6b8d4a6a03 ("Bluetooth: 6LoWPAN: Use connected oriented channel instead of fixed one")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

net/bluetooth/6lowpan.c

@@ -825,11 +825,16 @@ static struct sk_buff *chan_alloc_skb_cb(struct l2cap_chan *chan,
 					 unsigned long hdr_len,
 					 unsigned long len, int nb)
 {
+	struct sk_buff *skb;
+
 	/* Note that we must allocate using GFP_ATOMIC here as
 	 * this function is called originally from netdev hard xmit
 	 * function in atomic context.
 	 */
-	return bt_skb_alloc(hdr_len + len, GFP_ATOMIC);
+	skb = bt_skb_alloc(hdr_len + len, GFP_ATOMIC);
+	if (!skb)
+		return ERR_PTR(-ENOMEM);
+	return skb;
 }
 
 static void chan_suspend_cb(struct l2cap_chan *chan)