net: phy: marvell: Fix buffer overrun with stats counters

[ Upstream commit fdfdf86720a34527f777cbe0d8599bf0528fa146 ]

marvell_get_sset_count() returns how many statistics counters there
are. If the PHY supports fibre, there are 3, otherwise two.

marvell_get_strings() does not make this distinction, and always
returns 3 strings. This then often results in writing past the end
of the buffer for the strings.

Fixes: 2170fef78a40 ("Marvell phy: add field to get errors from fiber link.")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/phy/marvell.c

@@ -1513,9 +1513,10 @@ static int marvell_get_sset_count(struct phy_device *phydev)
 
 static void marvell_get_strings(struct phy_device *phydev, u8 *data)
 {
+	int count = marvell_get_sset_count(phydev);
 	int i;
 
-	for (i = 0; i < ARRAY_SIZE(marvell_hw_stats); i++) {
+	for (i = 0; i < count; i++) {
 		strlcpy(data + i * ETH_GSTRING_LEN,
 			marvell_hw_stats[i].string, ETH_GSTRING_LEN);
 	}
@@ -1543,9 +1544,10 @@ static u64 marvell_get_stat(struct phy_device *phydev, int i)
 static void marvell_get_stats(struct phy_device *phydev,
 			      struct ethtool_stats *stats, u64 *data)
 {
+	int count = marvell_get_sset_count(phydev);
 	int i;
 
-	for (i = 0; i < ARRAY_SIZE(marvell_hw_stats); i++)
+	for (i = 0; i < count; i++)
 		data[i] = marvell_get_stat(phydev, i);
 }