caif: fix a potential NULL dereference

Commit bd30ce4b (caif: Use RCU instead of spin-lock in caif_dev.c)
added a potential NULL dereference in case alloc_percpu() fails.

caif_device_alloc() can also use GFP_KERNEL instead of GFP_ATOMIC.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Sjur Brændeland <sjur.brandeland@stericsson.com>
Acked-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/caif/caif_dev.c

@@ -93,10 +93,14 @@ static struct caif_device_entry *caif_device_alloc(struct net_device *dev)
 	caifdevs = caif_device_list(dev_net(dev));
 	BUG_ON(!caifdevs);
 
-	caifd = kzalloc(sizeof(*caifd), GFP_ATOMIC);
+	caifd = kzalloc(sizeof(*caifd), GFP_KERNEL);
 	if (!caifd)
 		return NULL;
 	caifd->pcpu_refcnt = alloc_percpu(int);
+	if (!caifd->pcpu_refcnt) {
+		kfree(caifd);
+		return NULL;
+	}
 	caifd->netdev = dev;
 	dev_hold(dev);
 	return caifd;