From aa5c81f01f410be553a8c0c1ba7b167ec1cae314 Mon Sep 17 00:00:00 2001
From: Jose Abreu <Jose.Abreu@synopsys.com>
Date: Wed, 18 Dec 2019 11:17:37 +0100
Subject: [PATCH 07/10] net: stmmac: Do not accept invalid MTU values
Git-commit: eaf4fac478077d4ed57cbca2c044c4b58a96bd98
References: git-fixes
Patch-mainline: v5.5-rc3

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>
Acked-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 428222f3b480..7a785c1f63a1 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3626,12 +3626,24 @@ 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);
-- 
2.16.4