From 23609bce9e1de525d1d0e73fc68c6e7971d0b49e Mon Sep 17 00:00:00 2001 From: Haishuang Yan Date: Wed, 30 Sep 2026 20:48:18 +0800 Subject: [PATCH] pfcp: make sure the SEID is linear before reading it pfcp_encap_recv() only makes sure that the UDP header and the 4 byte PFCP header are in the linear area. When the S flag is set, pfcp_session_recv() then reads the 8 byte SEID that follows, which is not covered by the pskb_may_pull() check. A short PFCP packet with the S flag set, or one whose session header lies in a fragment, therefore makes pfcp_session_recv() read beyond the end of the packet data, and whatever it finds there is stored in the tunnel metadata that flower later classifies on. Pull up to the end of the SEID before reading it, and drop packets that are too short to contain it. Reload the header pointer afterwards since pskb_may_pull() may reallocate the skb head. Use offsetofend() rather than sizeof(struct pfcphdr_session): the structure is not packed, so its size is 16 bytes because of the alignment of the __be64 member, while the header on the wire is only 12 bytes, and valid session messages would be dropped. Fixes: 6dd514f48110 ("pfcp: always set pfcp metadata") Signed-off-by: Haishuang Yan Link: https://patch.msgid.link/20260930124818.114224-3-yanhaishuang@cmss.chinamobile.com Signed-off-by: Jakub Kicinski --- drivers/net/pfcp.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/net/pfcp.c b/drivers/net/pfcp.c index 3ecd43cafdf0..51c67c914fad 100644 --- a/drivers/net/pfcp.c +++ b/drivers/net/pfcp.c @@ -65,6 +65,13 @@ static int pfcp_encap_recv(struct sock *sk, struct sk_buff *skb) goto drop; unparsed = pfcp_hdr(skb); + if (unparsed->flags & PFCP_SEID_FLAG) { + if (unlikely(!pskb_may_pull(skb, PFCP_HLEN + + offsetofend(struct pfcphdr_session, + seid)))) + goto drop; + unparsed = pfcp_hdr(skb); + } ip_tunnel_flags_zero(flags); tun_dst = udp_tun_rx_dst(skb, sk->sk_family, flags, 0,