net/core: Fix potential memory leak in dev_set_alias()

[ Upstream commit 7364e445 ]

Do not leak memory by updating pointer with potentially NULL realloc return value.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

net/core/dev.c

@@ -967,6 +967,8 @@ int dev_change_name(struct net_device *dev, const char *newname)
  */
 int dev_set_alias(struct net_device *dev, const char *alias, size_t len)
 {
+	char *new_ifalias;
+
 	ASSERT_RTNL();
 
 	if (len >= IFALIASZ)
@@ -980,9 +982,10 @@ int dev_set_alias(struct net_device *dev, const char *alias, size_t len)
 		return 0;
 	}
 
-	dev->ifalias = krealloc(dev->ifalias, len + 1, GFP_KERNEL);
-	if (!dev->ifalias)
+	new_ifalias = krealloc(dev->ifalias, len + 1, GFP_KERNEL);
+	if (!new_ifalias)
 		return -ENOMEM;
+	dev->ifalias = new_ifalias;
 
 	strlcpy(dev->ifalias, alias, len+1);
 	return len;