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macvlan: inherit needed_headroom and needed_tailroom from lowerdev

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[ Upstream commit cef51860be ]

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: b863ceb7dd ("[NET]: Add macvlan driver")
Reported-by: Tangxin Xie <xietangxin@h-partners.com>
Closes: https://lore.kernel.org/netdev/CANn89i+1EW-sFNK8xoq98gMbPCeLS7e=+rs9gHfLg5Wj+4x0sw@mail.gmail.com/T/#m16adf0ff972cbfd8066c3a8e656e75eaeb12d021
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>
Link: https://patch.msgid.link/20260806141938.287660-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Eric Dumazet
2026-08-23 14:20:05 +02:00
committed by Greg Kroah-Hartman
parent f3c17ff65f
commit 28afc87bd8
1 changed files with 4 additions and 0 deletions
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drivers/net/macvlan.c
+4
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@@ -940,6 +940,8 @@ static int macvlan_init(struct net_device *dev)
dev->hw_enc_features |= dev->features;
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);
@@ -1822,6 +1824,8 @@ 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;