CVE-2025-38572

In the Linux kernel, the following vulnerability has been resolved:

ipv6: reject malicious packets in ipv6gsosegment()

syzbot was able to craft a packet with very long IPv6 extension headers leading to an overflow of skb->transport_header.

This 16bit field has a limited range.

Add skbresettransportheadercareful() helper and use it from ipv6gsosegment()

WARNING: CPU: 0 PID: 5871 at ./include/linux/skbuff.h:3032 skbresettransportheader include/linux/skbuff.h:3032 [inline] WARNING: CPU: 0 PID: 5871 at ./include/linux/skbuff.h:3032 ipv6gsosegment+0x15e2/0x21e0 net/ipv6/ip6offload.c:151 Modules linked in: CPU: 0 UID: 0 PID: 5871 Comm: syz-executor211 Not tainted 6.16.0-rc6-syzkaller-g7abc678e3084 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:skbresettransportheader include/linux/skbuff.h:3032 [inline] RIP: 0010:ipv6gsosegment+0x15e2/0x21e0 net/ipv6/ip6offload.c:151 Call Trace: <TASK> skbmacgsosegment+0x31c/0x640 net/core/gso.c:53 nshgsosegment+0x54a/0xe10 net/nsh/nsh.c:110 skbmacgsosegment+0x31c/0x640 net/core/gso.c:53 _skbgsosegment+0x342/0x510 net/core/gso.c:124 skbgsosegment include/net/gso.h:83 [inline] validatexmitskb+0x857/0x11b0 net/core/dev.c:3950 validatexmitskblist+0x84/0x120 net/core/dev.c:4000 schdirectxmit+0xd3/0x4b0 net/sched/schgeneric.c:329 _devxmitskb net/core/dev.c:4102 [inline] _devqueue_xmit+0x17b6/0x3a70 net/core/dev.c:4679