From: Eric Dumazet Date: Thu, 6 Aug 2026 14:19:38 +0000 (+0000) Subject: macvlan: inherit needed_headroom and needed_tailroom from lowerdev X-Git-Tag: v7.2~27^2~26 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cef51860becd9700217c81732ca1eb1ea6ed6fe1;p=thirdparty%2Fkernel%2Flinux.git macvlan: inherit needed_headroom and needed_tailroom from lowerdev macvlan devices inherit hard_header_len from lowerdev during macvlan_init(), but leave needed_headroom and needed_tailroom set to 0. When the underlying lowerdev requires extra headroom or tailroom for headers/trailers (e.g. macsec, ipsec, wireguard, tunnels, or veth with rx headroom), upper layers calculating packet headroom and tailroom fail to reserve sufficient space. This can result in reallocation overhead, skb headroom underflows, or KASAN slab-use-after-free crashes when dev_hard_header() / macvlan_hard_header() prepends header data or when lower devices append tailroom. Fix this by: 1. Inheriting needed_headroom and needed_tailroom from lowerdev in macvlan_init(). 2. Propagating needed_headroom and needed_tailroom updates to attached macvlans in macvlan_device_event() when receiving NETDEV_FEAT_CHANGE events. Fixes: b863ceb7ddce ("[NET]: Add macvlan driver") Reported-by: Tangxin Xie Closes: https://lore.kernel.org/netdev/CANn89i+1EW-sFNK8xoq98gMbPCeLS7e=+rs9gHfLg5Wj+4x0sw@mail.gmail.com/T/#m16adf0ff972cbfd8066c3a8e656e75eaeb12d021 Signed-off-by: Eric Dumazet Reviewed-by: Hangbin Liu Link: https://patch.msgid.link/20260806141938.287660-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c index c40fa331836b..ff2f4bb651b7 100644 --- a/drivers/net/macvlan.c +++ b/drivers/net/macvlan.c @@ -950,6 +950,8 @@ static int macvlan_init(struct net_device *dev) dev->lltx = true; netif_inherit_tso_max(dev, lowerdev); dev->hard_header_len = lowerdev->hard_header_len; + dev->needed_headroom = lowerdev->needed_headroom; + dev->needed_tailroom = lowerdev->needed_tailroom; macvlan_set_lockdep_class(dev); vlan->pcpu_stats = netdev_alloc_pcpu_stats(struct vlan_pcpu_stats); @@ -1824,6 +1826,8 @@ static int macvlan_device_event(struct notifier_block *unused, case NETDEV_FEAT_CHANGE: list_for_each_entry(vlan, &port->vlans, list) { netif_inherit_tso_max(vlan->dev, dev); + vlan->dev->needed_headroom = dev->needed_headroom; + vlan->dev->needed_tailroom = dev->needed_tailroom; netdev_update_features(vlan->dev); } break;