From 168ff39e4758897d2eee4756977d036d52884c7e Mon Sep 17 00:00:00 2001 From: Fernando Fernandez Mancera Date: Wed, 4 Mar 2026 13:03:57 +0100 Subject: net: vxlan: fix nd_tbl NULL dereference when IPv6 is disabled When booting with the 'ipv6.disable=1' parameter, the nd_tbl is never initialized because inet6_init() exits before ndisc_init() is called which initializes it. If an IPv6 packet is injected into the interface, route_shortcircuit() is called and a NULL pointer dereference happens on neigh_lookup(). BUG: kernel NULL pointer dereference, address: 0000000000000380 Oops: Oops: 0000 [#1] SMP NOPTI [...] RIP: 0010:neigh_lookup+0x20/0x270 [...] Call Trace: vxlan_xmit+0x638/0x1ef0 [vxlan] dev_hard_start_xmit+0x9e/0x2e0 __dev_queue_xmit+0xbee/0x14e0 packet_sendmsg+0x116f/0x1930 __sys_sendto+0x1f5/0x200 __x64_sys_sendto+0x24/0x30 do_syscall_64+0x12f/0x1590 entry_SYSCALL_64_after_hwframe+0x76/0x7e Fix this by adding an early check on route_shortcircuit() when protocol is ETH_P_IPV6. Note that ipv6_mod_enabled() cannot be used here because VXLAN can be built-in even when IPv6 is built as a module. Fixes: e15a00aafa4b ("vxlan: add ipv6 route short circuit support") Signed-off-by: Fernando Fernandez Mancera Link: https://patch.msgid.link/20260304120357.9778-2-fmancera@suse.de Signed-off-by: Jakub Kicinski --- drivers/net/vxlan/vxlan_core.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c index 05558b6afecd..17c941aac32d 100644 --- a/drivers/net/vxlan/vxlan_core.c +++ b/drivers/net/vxlan/vxlan_core.c @@ -2130,6 +2130,11 @@ static bool route_shortcircuit(struct net_device *dev, struct sk_buff *skb) { struct ipv6hdr *pip6; + /* check if nd_tbl is not initiliazed due to + * ipv6.disable=1 set during boot + */ + if (!ipv6_stub->nd_tbl) + return false; if (!pskb_may_pull(skb, sizeof(struct ipv6hdr))) return false; pip6 = ipv6_hdr(skb); -- cgit v1.2.3