CVE-2026-64577gtp: check skb_pull_data() return in gtp1u_send_echo_resp()

Official description

In the Linux kernel, the following vulnerability has been resolved: gtp: check skb_pull_data() return in gtp1u_send_echo_resp() gtp1u_send_echo_resp() ignores skb_pull_data()'s return value. Its caller gtp1u_udp_encap_recv() only guarantees 16 bytes (udphdr + gtp1_header), but the pull requests 20 (gtp1_header_long + udphdr). For a 16-19 byte echo request the pull fails and returns NULL without advancing skb->data; execution continues, and the following skb_push() plus the IP header pushed by iptunnel_xmit() move skb->data below skb->head, tripping skb_under_panic(). Fix it by dropping the packet when skb_pull_data() fails. skbuff: skb_under_panic: ... kernel BUG at net/core/skbuff.c:214! Call Trace: skb_push (net/core/skbuff.c:2648) iptunnel_xmit (net/ipv4/ip_tunnel_core.c:82) gtp_encap_recv (drivers/net/gtp.c:701 drivers/net/gtp.c:808 drivers/net/gtp.c:920) udp_queue_rcv_one_skb (net/ipv4/udp.c:2388) ... Kernel panic - not syncing: Fatal exception in interrupt

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/9033fe49926f0e7421fefee922dc086417e905cf
• https://git.kernel.org/stable/c/b3c733eaae7f362601c28ac1533d47a961cd3e1c
• https://git.kernel.org/stable/c/4fc7923871d176ce0e5fecf4a9b7bb915af790ed
• https://git.kernel.org/stable/c/961e9b1e33445f8e42859ecc020c9f60d8b69a8b
• https://git.kernel.org/stable/c/cf45d748e437b8dd2dd987f27ee79c8c86f95c88
• https://git.kernel.org/stable/c/cd170f051dba9ac146fabcd1b91726487c0cb9fa