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 ! 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

Affected Software

References

• https://git.kernel.org/stable/c/1717357007db150c2d703f13f5695460e960f26c
• https://git.kernel.org/stable/c/17e7386234f740f3e7d5e58a47b5847ea34c3bc2
• https://git.kernel.org/stable/c/41a1a3140aff295dee8063906f70a514548105e8
• https://git.kernel.org/stable/c/5fe210533e3459197eabfdbf97327dacbdc04d60
• https://git.kernel.org/stable/c/91a2b25be07ce1a7549ceebbe82017551d2eec92
• https://git.kernel.org/stable/c/adee129db814474f2f81207bd182bf343832a52e
• https://git.kernel.org/stable/c/db5b4e39c4e63700c68a7e65fc4e1f1375273476