CVE-2024-35973

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

geneve: fix header validation in geneve[6]_xmit_skb

syzbot is able to trigger an uninit-value in geneve_xmit() [1]

Problem : While most ip tunnel helpers (like ip_tunnel_get_dsfield())

uses skb_protocol(skb, true), pskb_inet_may_pull() is only using

skb->protocol.

If anything else than ETH_P_IPV6 or ETH_P_IP is found in skb->protocol,

pskb_inet_may_pull() does nothing at all.

If a vlan tag was provided by the caller (af_packet in the syzbot case),

the network header might not point to the correct location, and skb

linear part could be smaller than expected.

Add skb_vlan_inet_prepare() to perform a complete mac validation.

Use this in geneve for the moment, I suspect we need to adopt this

more broadly.

v4 - Jakub reported v3 broke l2_tos_ttl_inherit.sh selftest

- Only call __vlan_get_protocol() for vlan types.

v2,v3 - Addressed Sabrina comments on v1 and v2

[1]

BUG: KMSAN: uninit-value in geneve_xmit_skb drivers/net/geneve.c:910 [inline]

BUG: KMSAN: uninit-value in geneve_xmit+0x302d/0x5420 drivers/net/geneve.c:1030

geneve_xmit_skb drivers/net/geneve.c:910 [inline]

geneve_xmit+0x302d/0x5420 drivers/net/geneve.c:1030

__netdev_start_xmit include/linux/netdevice.h:4903 [inline]

netdev_start_xmit include/linux/netdevice.h:4917 [inline]

xmit_one net/core/dev.c:3531 [inline]

dev_hard_start_xmit+0x247/0xa20 net/core/dev.c:3547

__dev_queue_xmit+0x348d/0x52c0 net/core/dev.c:4335

dev_queue_xmit include/linux/netdevice.h:3091 [inline]

packet_xmit+0x9c/0x6c0 net/packet/af_packet.c:276

packet_snd net/packet/af_packet.c:3081 [inline]

packet_sendmsg+0x8bb0/0x9ef0 net/packet/af_packet.c:3113

sock_sendmsg_nosec net/socket.c:730 [inline]

__sock_sendmsg+0x30f/0x380 net/socket.c:745

__sys_sendto+0x685/0x830 net/socket.c:2191

__do_sys_sendto net/socket.c:2203 [inline]

__se_sys_sendto net/socket.c:2199 [inline]

__x64_sys_sendto+0x125/0x1d0 net/socket.c:2199

do_syscall_64+0xd5/0x1f0

entry_SYSCALL_64_after_hwframe+0x6d/0x75

Uninit was created at:

slab_post_alloc_hook mm/slub.c:3804 [inline]

slab_alloc_node mm/slub.c:3845 [inline]

kmem_cache_alloc_node+0x613/0xc50 mm/slub.c:3888

kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:577

__alloc_skb+0x35b/0x7a0 net/core/skbuff.c:668

alloc_skb include/linux/skbuff.h:1318 [inline]

alloc_skb_with_frags+0xc8/0xbf0 net/core/skbuff.c:6504

sock_alloc_send_pskb+0xa81/0xbf0 net/core/sock.c:2795

packet_alloc_skb net/packet/af_packet.c:2930 [inline]

packet_snd net/packet/af_packet.c:3024 [inline]

packet_sendmsg+0x722d/0x9ef0 net/packet/af_packet.c:3113

sock_sendmsg_nosec net/socket.c:730 [inline]

__sock_sendmsg+0x30f/0x380 net/socket.c:745

__sys_sendto+0x685/0x830 net/socket.c:2191

__do_sys_sendto net/socket.c:2203 [inline]

__se_sys_sendto net/socket.c:2199 [inline]

__x64_sys_sendto+0x125/0x1d0 net/socket.c:2199

do_syscall_64+0xd5/0x1f0

entry_SYSCALL_64_after_hwframe+0x6d/0x75

CPU: 0 PID: 5033 Comm: syz-executor346 Not tainted 6.9.0-rc1-syzkaller-00005-g928a87efa423 #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024