@@ -280,17 +280,20 @@ static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
struct ip_tunnel *tunnel = netdev_priv(dev);
struct flowi fl;
- if (!pskb_inet_may_pull(skb))
- goto tx_err;
-
memset(&fl, 0, sizeof(fl));
switch (skb->protocol) {
case htons(ETH_P_IP):
+ if (!pskb_network_may_pull(skb, sizeof(struct iphdr)))
+ goto tx_err;
+
memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
xfrm_decode_session(dev_net(dev), skb, &fl, AF_INET);
break;
case htons(ETH_P_IPV6):
+ if (!pskb_network_may_pull(skb, sizeof(struct ipv6hdr)))
+ goto tx_err;
+
memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
xfrm_decode_session(dev_net(dev), skb, &fl, AF_INET6);
break;
syzkaller demonstrated the underflow in pskb_network_may_pull() by sending a crafted VLAN packet over the tunnel device. Let's check skb->protocol before pulling the next header in vti_tunnel_xmit(). WARNING: CPU: 1 PID: 4534 at include/linux/skbuff.h:2740 pskb_may_pull_reason include/linux/skbuff.h:2740 [inline] WARNING: CPU: 1 PID: 4534 at include/linux/skbuff.h:2740 pskb_may_pull include/linux/skbuff.h:2756 [inline] WARNING: CPU: 1 PID: 4534 at include/linux/skbuff.h:2740 pskb_network_may_pull include/linux/skbuff.h:3077 [inline] WARNING: CPU: 1 PID: 4534 at include/linux/skbuff.h:2740 pskb_inet_may_pull include/net/ip_tunnels.h:361 [inline] WARNING: CPU: 1 PID: 4534 at include/linux/skbuff.h:2740 vti_tunnel_xmit+0xd48/0x14b4 net/ipv4/ip_vti.c:283 Modules linked in: CPU: 1 PID: 4534 Comm: syz-executor.1 Not tainted 6.8.0-12821-g537c2e91d354-dirty #11 Hardware name: linux,dummy-virt (DT) pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : pskb_may_pull_reason include/linux/skbuff.h:2740 [inline] pc : pskb_may_pull include/linux/skbuff.h:2756 [inline] pc : pskb_network_may_pull include/linux/skbuff.h:3077 [inline] pc : pskb_inet_may_pull include/net/ip_tunnels.h:361 [inline] pc : vti_tunnel_xmit+0xd48/0x14b4 net/ipv4/ip_vti.c:283 lr : pskb_may_pull_reason include/linux/skbuff.h:2740 [inline] lr : pskb_may_pull include/linux/skbuff.h:2756 [inline] lr : pskb_network_may_pull include/linux/skbuff.h:3077 [inline] lr : pskb_inet_may_pull include/net/ip_tunnels.h:361 [inline] lr : vti_tunnel_xmit+0xd48/0x14b4 net/ipv4/ip_vti.c:283 sp : ffff8000a99372a0 x29: ffff8000a99373e0 x28: ffff00000d188838 x27: ffff700015326e64 x26: ffff000061930080 x25: dfff800000000000 x24: ffff8000a9937320 x23: 0000000000000000 x22: ffff00000d188834 x21: 00000000fffffff6 x20: ffff00000d188780 x19: ffff000017580000 x18: ffff800086d72d10 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000001 x14: 1fffe000029ce017 x13: 0000000000000000 x12: 0000000000000001 x11: 0000000000040000 x10: 0000000000000b7f x9 : ffff80008a3fa000 x8 : 0000000000000b80 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff8000a9936c98 x4 : ffff800086d8b120 x3 : ffff800083f7f7d4 x2 : 0000000000000001 x1 : 00000000fffffff6 x0 : 0000000000000000 Call trace: pskb_may_pull_reason include/linux/skbuff.h:2740 [inline] pskb_may_pull include/linux/skbuff.h:2756 [inline] pskb_network_may_pull include/linux/skbuff.h:3077 [inline] pskb_inet_may_pull include/net/ip_tunnels.h:361 [inline] vti_tunnel_xmit+0xd48/0x14b4 net/ipv4/ip_vti.c:283 __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+0x1a0/0x370 net/core/dev.c:3547 __dev_queue_xmit+0x12e8/0x2b04 net/core/dev.c:4335 dev_queue_xmit include/linux/netdevice.h:3091 [inline] packet_xmit+0x6c/0x31c net/packet/af_packet.c:276 packet_snd net/packet/af_packet.c:3081 [inline] packet_sendmsg+0x3818/0x4e50 net/packet/af_packet.c:3113 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg net/socket.c:745 [inline] __sys_sendto+0x324/0x470 net/socket.c:2191 __do_sys_sendto net/socket.c:2203 [inline] __se_sys_sendto net/socket.c:2199 [inline] __arm64_sys_sendto+0xd8/0xf8 net/socket.c:2199 __invoke_syscall arch/arm64/kernel/syscall.c:34 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152 el0_svc+0x30/0x78 arch/arm64/kernel/entry-common.c:712 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598 Reported-by: syzkaller <syzkaller@googlegroups.com> Fixes: cb9f1b783850 ("ip: validate header length on virtual device xmit") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- net/ipv4/ip_vti.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)