dpaa2-eth: Fix potential spectre issue

[ Upstream commit 5a20a093 ]

Smatch reports a potential spectre vulnerability in the dpaa2-eth
driver, where the value of rxnfc->fs.location (which is provided
from user-space) is used as index in an array.

Add a call to array_index_nospec() to sanitize the access.
Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/ethernet/freescale/dpaa2/dpaa2-ethtool.c

@@ -4,6 +4,7 @@
  */
 
 #include <linux/net_tstamp.h>
+#include <linux/nospec.h>
 
 #include "dpni.h"	/* DPNI_LINK_OPT_* */
 #include "dpaa2-eth.h"
@@ -589,6 +590,8 @@ static int dpaa2_eth_get_rxnfc(struct net_device *net_dev,
 	case ETHTOOL_GRXCLSRULE:
 		if (rxnfc->fs.location >= max_rules)
 			return -EINVAL;
+		rxnfc->fs.location = array_index_nospec(rxnfc->fs.location,
+							max_rules);
 		if (!priv->cls_rules[rxnfc->fs.location].in_use)
 			return -EINVAL;
 		rxnfc->fs = priv->cls_rules[rxnfc->fs.location].fs;