CVE-2025-71098

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

ip6_gre: make ip6gre_header() robust

Over the years, syzbot found many ways to crash the kernel

in ip6gre_header() [1].

This involves team or bonding drivers ability to dynamically

change their dev->needed_headroom and/or dev->hard_header_len

In this particular crash mld_newpack() allocated an skb

with a too small reserve/headroom, and by the time mld_sendpack()

was called, syzbot managed to attach an ip6gre device.

[1]

skbuff: skb_under_panic: text:ffffffff8a1d69a8 len:136 put:40 head:ffff888059bc7000 data:ffff888059bc6fe8 tail:0x70 end:0x6c0 dev:team0

------------[ cut here ]------------

kernel BUG at net/core/skbuff.c:213 !

<TASK>

skb_under_panic net/core/skbuff.c:223 [inline]

skb_push+0xc3/0xe0 net/core/skbuff.c:2641

ip6gre_header+0xc8/0x790 net/ipv6/ip6_gre.c:1371

dev_hard_header include/linux/netdevice.h:3436 [inline]

neigh_connected_output+0x286/0x460 net/core/neighbour.c:1618

neigh_output include/net/neighbour.h:556 [inline]

ip6_finish_output2+0xfb3/0x1480 net/ipv6/ip6_output.c:136

__ip6_finish_output net/ipv6/ip6_output.c:-1 [inline]

ip6_finish_output+0x234/0x7d0 net/ipv6/ip6_output.c:220

NF_HOOK_COND include/linux/netfilter.h:307 [inline]

ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247

NF_HOOK+0x9e/0x380 include/linux/netfilter.h:318

mld_sendpack+0x8d4/0xe60 net/ipv6/mcast.c:1855

mld_send_cr net/ipv6/mcast.c:2154 [inline]

mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2693