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In v3 I asked that the commit message: 1. State that the overlay and underlay devices should be of the same type (both erspan or both ip6erspan) for the splat to happen. 2. Mention the IPv6 fix. Currently you only describe the IPv4 path: erspan_xmit() -> ip_tunnel_xmit() https://lore.kernel.org/netdev/20260803151146.GA766007@shredder/ > > Reported-by: syzbot+9bda1b9fbb7fbdf9b62b@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=9bda1b9fbb7fbdf9b62b > Fixes: 84e54fe0a5ea ("gre: introduce native tunnel support for ERSPAN") > Fixes: 5a963eb61b7c ("ip6_gre: Add ERSPAN native tunnel support") > Cc: stable@vger.kernel.org > Signed-off-by: Yun Zhou > --- > v4: > - refine commit message > > v3: > - add fix for IPv6 > > v2: > - change subject prefix to [PATCH net] > > net/ipv4/ip_gre.c | 2 ++ > net/ipv6/ip6_gre.c | 2 ++ > 2 files changed, 4 insertions(+) > > diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c > index 82309efd417e..0058cb20e36a 100644 > --- a/net/ipv4/ip_gre.c > +++ b/net/ipv4/ip_gre.c > @@ -1367,6 +1367,8 @@ static int erspan_tunnel_init(struct net_device *dev) > dev->features |= GRE_FEATURES; > dev->hw_features |= GRE_FEATURES; > dev->priv_flags |= IFF_LIVE_ADDR_CHANGE; > + /* Skip TX lock: xmit re-enters stack, risking ABBA with underlay */ Nit: I would drop this comment. It doesn't add anything and we don't have it above similar assignments in the file. > + dev->lltx = true; > netif_keep_dst(dev); > > return ip_tunnel_init(dev); > diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c > index 8ebda0b6a78b..578fb3475f8c 100644 > --- a/net/ipv6/ip6_gre.c > +++ b/net/ipv6/ip6_gre.c > @@ -1871,6 +1871,8 @@ static int ip6erspan_tap_init(struct net_device *dev) > dev->mtu -= 8; > > dev->priv_flags |= IFF_LIVE_ADDR_CHANGE; > + /* Skip TX lock: xmit re-enters stack, risking ABBA with underlay */ Same. > + dev->lltx = true; > ip6erspan_tnl_link_config(tunnel, 1); > > netdev_hold(dev, &tunnel->dev_tracker, GFP_KERNEL); > -- > 2.43.0 >