net: stmmac: Do not accept invalid MTU values

The maximum MTU value is determined by the maximum size of TX FIFO so
that a full packet can fit in the FIFO. Add a check for this in the MTU
change callback.

Also check if provided and rounded MTU does not passes the maximum limit
of 16K.

Changes from v2:
- Align MTU before checking if its valid

Fixes: 7ac6653a085b ("stmmac: Move the STMicroelectronics driver")
Signed-off-by: Jose Abreu <Jose.Abreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index eccbf5d..8b78619 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3827,12 +3827,24 @@ static void stmmac_set_rx_mode(struct net_device *dev)
 static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
 {
        struct stmmac_priv *priv = netdev_priv(dev);
+       int txfifosz = priv->plat->tx_fifo_size;
+
+       if (txfifosz == 0)
+               txfifosz = priv->dma_cap.tx_fifo_size;
+
+       txfifosz /= priv->plat->tx_queues_to_use;
 
        if (netif_running(dev)) {
                netdev_err(priv->dev, "must be stopped to change its MTU\n");
                return -EBUSY;
        }
 
+       new_mtu = STMMAC_ALIGN(new_mtu);
+
+       /* If condition true, FIFO is too small or MTU too large */
+       if ((txfifosz < new_mtu) || (new_mtu > BUF_SIZE_16KiB))
+               return -EINVAL;
+
        dev->mtu = new_mtu;
 
        netdev_update_features(dev);