7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 8ec454dcd00ce3375119111c6394964455b36d0d ] Since commit d58e468b1112 ("flow_dissector: implements flow dissector BPF hook") __skb_flow_dissect() needs a net pointer, either from skb->dev, skb->sk, or since commit 3cbf4ffba5ee ("net: plumb network namespace into __skb_flow_dissect") a caller provided pointer. syzbot was able to reach seg6_make_flowlabel() with an skb having neither skb->dev nor skb->sk set: a TIPC UDP bearer sends a discovery message through an IPv4 route using seg6 encap, while net.ipv6.seg6_flowlabel is set to 1. seg6_make_flowlabel() already has a net pointer, use skb_get_hash_net(). WARNING: net/core/flow_dissector.c:1131 at __skb_flow_dissect+0x910/0x5368 net/core/flow_dissector.c:1126, CPU#0: syz.0.17/4930 Call trace: __skb_flow_dissect+0x910/0x5368 net/core/flow_dissector.c:1126 (P) __skb_get_hash_net+0xe0/0x29c net/core/flow_dissector.c:1903 skb_get_hash include/linux/skbuff.h:1663 [inline] seg6_make_flowlabel+0xcc/0x1ec net/ipv6/seg6_iptunnel.c:132 __seg6_do_srh_encap+0x320/0xbf4 net/ipv6/seg6_iptunnel.c:161 seg6_do_srh+0x4b4/0xa44 net/ipv6/seg6_iptunnel.c:431 seg6_output_core+0x164/0x688 net/ipv6/seg6_iptunnel.c:681 seg6_output+0x44/0x1ac net/ipv6/seg6_iptunnel.c:744 lwtunnel_output+0x3d0/0x664 net/core/lwtunnel.c:356 dst_output include/net/dst.h:470 [inline] ip_local_out+0x110/0x148 net/ipv4/ip_output.c:131 iptunnel_xmit+0x50c/0xd38 net/ipv4/ip_tunnel_core.c:97 udp_tunnel_xmit_skb+0x220/0x348 net/ipv4/udp_tunnel_core.c:187 tipc_udp_xmit+0x75c/0x9c0 net/tipc/udp_media.c:202 tipc_udp_send_msg+0x214/0x374 net/tipc/udp_media.c:274 tipc_bearer_xmit_skb+0x260/0x3b0 net/tipc/bearer.c:576 tipc_enable_bearer net/tipc/bearer.c:366 [inline] __tipc_nl_bearer_enable+0xc90/0xfb0 net/tipc/bearer.c:1048 tipc_nl_bearer_enable+0x2c/0x48 net/tipc/bearer.c:1057 genl_family_rcv_msg_doit+0x1e4/0x2d4 net/netlink/genetlink.c:1114 Fixes: d58e468b1112 ("flow_dissector: implements flow dissector BPF hook") Reported-by: syzbot+9408fbe0e6452a12e9ab@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6abac2eb.3654fce1.1bec97.0000.GAE@google.com/ Signed-off-by: Eric Dumazet Reviewed-by: Xuanqiang Luo Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260928194524.3617299-1-edumazet@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv6/seg6_iptunnel.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c index 4c45c0a77d75d..73422a2730809 100644 --- a/net/ipv6/seg6_iptunnel.c +++ b/net/ipv6/seg6_iptunnel.c @@ -127,7 +127,7 @@ static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb, u32 hash; if (do_flowlabel > 0) { - hash = skb_get_hash(skb); + hash = skb_get_hash_net(net, skb); hash = rol32(hash, 16); flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK; } else if (!do_flowlabel && skb->protocol == htons(ETH_P_IPV6)) { -- 2.53.0