net: annotate writes on dev->mtu from ndo_change_mtu()

Simon reported that ndo_change_mtu() methods were never
updated to use WRITE_ONCE(dev->mtu, new_mtu) as hinted
in commit 501a90c94510 ("inet: protect against too small
mtu values.")

We read dev->mtu without holding RTNL in many places,
with READ_ONCE() annotations.

It is time to take care of ndo_change_mtu() methods
to use corresponding WRITE_ONCE()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Simon Horman <horms@kernel.org>
Closes: https://lore.kernel.org/netdev/20240505144608.GB67882@kernel.org/
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Shannon Nelson <shannon.nelson@amd.com>
Link: https://lore.kernel.org/r/20240506102812.3025432-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

6 files changed, 7 insertions, 7 deletions

diff --git a/drivers/net/ethernet/broadcom/b44.c b/drivers/net/ethernet/broadcom/b44.c
index 1be6d14030bc..e5809ad5eb82 100644
--- a/drivers/net/ethernet/broadcom/b44.c
+++ b/drivers/net/ethernet/broadcom/b44.c
@@ -1042,13 +1042,13 @@ static int b44_change_mtu(struct net_device *dev, int new_mtu)
 		/* We'll just catch it later when the
 		 * device is up'd.
 		 */
-		dev->mtu = new_mtu;
+		WRITE_ONCE(dev->mtu, new_mtu);
 		return 0;
 	}
 
 	spin_lock_irq(&bp->lock);
 	b44_halt(bp);
-	dev->mtu = new_mtu;
+	WRITE_ONCE(dev->mtu, new_mtu);
 	b44_init_rings(bp);
 	b44_init_hw(bp, B44_FULL_RESET);
 	spin_unlock_irq(&bp->lock);
diff --git a/drivers/net/ethernet/broadcom/bcm63xx_enet.c b/drivers/net/ethernet/broadcom/bcm63xx_enet.c
index 3196c4dea076..3c0e3b9828be 100644
--- a/drivers/net/ethernet/broadcom/bcm63xx_enet.c
+++ b/drivers/net/ethernet/broadcom/bcm63xx_enet.c
@@ -1652,7 +1652,7 @@ static int bcm_enet_change_mtu(struct net_device *dev, int new_mtu)
 	priv->rx_frag_size = SKB_DATA_ALIGN(priv->rx_buf_offset + priv->rx_buf_size) +
 					    SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 
-	dev->mtu = new_mtu;
+	WRITE_ONCE(dev->mtu, new_mtu);
 	return 0;
 }
 
diff --git a/drivers/net/ethernet/broadcom/bnx2.c b/drivers/net/ethernet/broadcom/bnx2.c
index b65b8592ad75..6ec773e61182 100644
--- a/drivers/net/ethernet/broadcom/bnx2.c
+++ b/drivers/net/ethernet/broadcom/bnx2.c
@@ -7912,7 +7912,7 @@ bnx2_change_mtu(struct net_device *dev, int new_mtu)
 {
 	struct bnx2 *bp = netdev_priv(dev);
 
-	dev->mtu = new_mtu;
+	WRITE_ONCE(dev->mtu, new_mtu);
 	return bnx2_change_ring_size(bp, bp->rx_ring_size, bp->tx_ring_size,
 				     false);
 }
diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
index c9b6acd8c892..a8e07e51418f 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
@@ -4902,7 +4902,7 @@ int bnx2x_change_mtu(struct net_device *dev, int new_mtu)
 	 * because the actual alloc size is
 	 * only updated as part of load
 	 */
-	dev->mtu = new_mtu;
+	WRITE_ONCE(dev->mtu, new_mtu);
 
 	if (!bnx2x_mtu_allows_gro(new_mtu))
 		dev->features &= ~NETIF_F_GRO_HW;
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 0d1ed6e5dfbd..c437ca1c0fd3 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -14280,7 +14280,7 @@ static int bnxt_change_mtu(struct net_device *dev, int new_mtu)
 	if (netif_running(dev))
 		bnxt_close_nic(bp, true, false);
 
-	dev->mtu = new_mtu;
+	WRITE_ONCE(dev->mtu, new_mtu);
 	bnxt_set_ring_params(bp);
 
 	if (netif_running(dev))
diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index e6ff3c9bd7e5..1589a49b876c 100644
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -14295,7 +14295,7 @@ static void tg3_set_rx_mode(struct net_device *dev)
 static inline void tg3_set_mtu(struct net_device *dev, struct tg3 *tp,
 			       int new_mtu)
 {
-	dev->mtu = new_mtu;
+	WRITE_ONCE(dev->mtu, new_mtu);
 
 	if (new_mtu > ETH_DATA_LEN) {
 		if (tg3_flag(tp, 5780_CLASS)) {