From 1eb2cded45b35816085c1f962933c187d970f9dc Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 6 May 2024 10:28:12 +0000 Subject: [PATCH] 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 Reported-by: Simon Horman Closes: https://lore.kernel.org/netdev/20240505144608.GB67882@kernel.org/ Reviewed-by: Jacob Keller Reviewed-by: Sabrina Dubroca Reviewed-by: Simon Horman Acked-by: Shannon Nelson Link: https://lore.kernel.org/r/20240506102812.3025432-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/realtek/8139cp.c | 4 ++-- drivers/net/ethernet/realtek/r8169_main.c | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) --- a/drivers/net/ethernet/realtek/8139cp.c +++ b/drivers/net/ethernet/realtek/8139cp.c @@ -1277,14 +1277,14 @@ static int cp_change_mtu(struct net_devi /* if network interface not up, no need for complexity */ if (!netif_running(dev)) { - dev->mtu = new_mtu; + WRITE_ONCE(dev->mtu, new_mtu); cp_set_rxbufsize(cp); /* set new rx buf size */ return 0; } /* network IS up, close it, reset MTU, and come up again. */ cp_close(dev); - dev->mtu = new_mtu; + WRITE_ONCE(dev->mtu, new_mtu); cp_set_rxbufsize(cp); return cp_open(dev); } --- a/drivers/net/ethernet/realtek/r8169_main.c +++ b/drivers/net/ethernet/realtek/r8169_main.c @@ -3952,7 +3952,7 @@ static int rtl8169_change_mtu(struct net { struct rtl8169_private *tp = netdev_priv(dev); - dev->mtu = new_mtu; + WRITE_ONCE(dev->mtu, new_mtu); netdev_update_features(dev); rtl_jumbo_config(tp); rtl_set_eee_txidle_timer(tp);