From c38b8f5f791ecce13ab77e2257f8fd2444ba80f6 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 12 Mar 2026 04:39:08 +0000 Subject: [PATCH] net: prevent NULL deref in ip[6]tunnel_xmit() Blamed commit missed that both functions can be called with dev == NULL. Also add unlikely() hints for these conditions that only fuzzers can hit. Fixes: 6f1a9140ecda ("net: add xmit recursion limit to tunnel xmit functions") Signed-off-by: Eric Dumazet CC: Weiming Shi Link: https://patch.msgid.link/20260312043908.2790803-1-edumazet@google.com Signed-off-by: Paolo Abeni --- include/net/ip6_tunnel.h | 10 ++++++---- net/ipv4/ip_tunnel_core.c | 10 ++++++---- 2 files changed, 12 insertions(+), 8 deletions(-) diff --git a/include/net/ip6_tunnel.h b/include/net/ip6_tunnel.h index 1253cbb4b0a4..359b595f1df9 100644 --- a/include/net/ip6_tunnel.h +++ b/include/net/ip6_tunnel.h @@ -156,10 +156,12 @@ static inline void ip6tunnel_xmit(struct sock *sk, struct sk_buff *skb, { int pkt_len, err; - if (dev_recursion_level() > IP_TUNNEL_RECURSION_LIMIT) { - net_crit_ratelimited("Dead loop on virtual device %s, fix it urgently!\n", - dev->name); - DEV_STATS_INC(dev, tx_errors); + if (unlikely(dev_recursion_level() > IP_TUNNEL_RECURSION_LIMIT)) { + if (dev) { + net_crit_ratelimited("Dead loop on virtual device %s, fix it urgently!\n", + dev->name); + DEV_STATS_INC(dev, tx_errors); + } kfree_skb(skb); return; } diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c index b1b6bf949f65..5683c328990f 100644 --- a/net/ipv4/ip_tunnel_core.c +++ b/net/ipv4/ip_tunnel_core.c @@ -58,10 +58,12 @@ void iptunnel_xmit(struct sock *sk, struct rtable *rt, struct sk_buff *skb, struct iphdr *iph; int err; - if (dev_recursion_level() > IP_TUNNEL_RECURSION_LIMIT) { - net_crit_ratelimited("Dead loop on virtual device %s, fix it urgently!\n", - dev->name); - DEV_STATS_INC(dev, tx_errors); + if (unlikely(dev_recursion_level() > IP_TUNNEL_RECURSION_LIMIT)) { + if (dev) { + net_crit_ratelimited("Dead loop on virtual device %s, fix it urgently!\n", + dev->name); + DEV_STATS_INC(dev, tx_errors); + } ip_rt_put(rt); kfree_skb(skb); return;