octeontx2-pf: fix a buffer overflow in otx2_set_rxfh_context()

This function is called from ethtool_set_rxfh() and "*rss_context"
comes from the user.  Add some bounds checking to prevent memory
corruption.

Fixes: 81a43620 ("octeontx2-pf: Add RSS multi group support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c

@@ -786,6 +786,10 @@ static int otx2_set_rxfh_context(struct net_device *dev, const u32 *indir,
 	if (hfunc != ETH_RSS_HASH_NO_CHANGE && hfunc != ETH_RSS_HASH_TOP)
 		return -EOPNOTSUPP;
 
+	if (*rss_context != ETH_RXFH_CONTEXT_ALLOC &&
+	    *rss_context >= MAX_RSS_GROUPS)
+		return -EINVAL;
+
 	rss = &pfvf->hw.rss_info;
 
 	if (!rss->enable) {