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Miller" , Jakub Kicinski , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, eric.dumazet@gmail.com, syzbot+1f9fd0f4b601cf88d6e6@syzkaller.appspotmail.com, Tangxin Xie Subject: Re: [PATCH v2 net] ipvlan: inherit needed_headroom and needed_tailroom from phy_dev Message-ID: References: <20260806103857.115541-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline In-Reply-To: <20260806103857.115541-1-edumazet@google.com> On 06.08.2026 10:38, Eric Dumazet wrote: >ipvlan devices inherit hard_header_len from phy_dev during ipvlan_init(), >but leave needed_headroom and needed_tailroom set to 0. > >When the underlying phy_dev (or stacked lower device) 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() / ipvlan_hard_header() >prepends header data or when lower devices append tailroom. > >Fix this by: >1. Inheriting needed_headroom and needed_tailroom from phy_dev in ipvlan_init(). >2. Propagating needed_headroom and needed_tailroom updates to attached ipvlans > in ipvlan_device_event() when receiving NETDEV_FEAT_CHANGE events. > >Fixes: 2ad7bfab3016 ("ipvlan: Initial check-in of the IPVLAN driver.") >Reported-by: syzbot+1f9fd0f4b601cf88d6e6@syzkaller.appspotmail.com >Closes: https://lore.kernel.org/netdev/6a720a21.40259c87.584f4.04bb.GAE@google.com/T/#u >Reported-by: Tangxin Xie >Closes: https://lore.kernel.org/netdev/CANn89i+1EW-sFNK8xoq98gMbPCeLS7e=+rs9gHfLg5Wj+4x0sw@mail.gmail.com/T/#mcc6307f115e500df23ea2980d5669fe95f20b6b4 >Signed-off-by: Eric Dumazet >--- >v2: also inherit needed_tailroom (Sashiko) >v1: https://lore.kernel.org/netdev/CANn89iLr4EQxBAKikZCeXbXEk-pjmT4mq3d=D2P01MtNSUgwrg@mail.gmail.com/T/#t > > drivers/net/ipvlan/ipvlan_main.c | 4 ++++ > 1 file changed, 4 insertions(+) > >diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c >index ed46439a9f4eb1dd8bfaf6c83476ba4f2aff31bc..92d3d340281ffbc8e54a61e975484ab156c42c9b 100644 >--- a/drivers/net/ipvlan/ipvlan_main.c >+++ b/drivers/net/ipvlan/ipvlan_main.c >@@ -146,6 +146,8 @@ static int ipvlan_init(struct net_device *dev) > dev->lltx = true; > netif_inherit_tso_max(dev, phy_dev); > dev->hard_header_len = phy_dev->hard_header_len; >+ dev->needed_headroom = phy_dev->needed_headroom; >+ dev->needed_tailroom = phy_dev->needed_tailroom; > > netdev_lockdep_set_classes(dev); > >@@ -773,6 +775,8 @@ static int ipvlan_device_event(struct notifier_block *unused, > case NETDEV_FEAT_CHANGE: > list_for_each_entry(ipvlan, &port->ipvlans, pnode) { > netif_inherit_tso_max(ipvlan->dev, dev); >+ ipvlan->dev->needed_headroom = dev->needed_headroom; >+ ipvlan->dev->needed_tailroom = dev->needed_tailroom; > netdev_update_features(ipvlan->dev); > } > break; >-- >2.55.0.629.g250fe7f194-goog > Reviewed-by: Hangbin Liu