netdev - [PATCH v1 net 4/5] ipip: Pull header after checking skb->protocol in ipip_tunnel

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Message-ID: <20240415222041.18537-5-kuniyu@amazon.com>
Date: Mon, 15 Apr 2024 15:20:40 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, David Ahern <dsahern@...nel.org>
CC: Steffen Klassert <steffen.klassert@...unet.com>, Herbert Xu
	<herbert@...dor.apana.org.au>, Willem de Bruijn <willemb@...gle.com>,
	Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima
	<kuni1840@...il.com>, <netdev@...r.kernel.org>, syzkaller
	<syzkaller@...glegroups.com>
Subject: [PATCH v1 net 4/5] ipip: Pull header after checking skb->protocol in ipip_tunnel_xmit().

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
ipip_tunnel_xmit().

WARNING: CPU: 0 PID: 4406 at include/linux/skbuff.h:2740 pskb_may_pull_reason include/linux/skbuff.h:2740 [inline]
WARNING: CPU: 0 PID: 4406 at include/linux/skbuff.h:2740 pskb_may_pull include/linux/skbuff.h:2756 [inline]
WARNING: CPU: 0 PID: 4406 at include/linux/skbuff.h:2740 pskb_network_may_pull include/linux/skbuff.h:3077 [inline]
WARNING: CPU: 0 PID: 4406 at include/linux/skbuff.h:2740 pskb_inet_may_pull include/net/ip_tunnels.h:361 [inline]
WARNING: CPU: 0 PID: 4406 at include/linux/skbuff.h:2740 ipip_tunnel_xmit+0x2d4/0x430 net/ipv4/ipip.c:281
Modules linked in:
CPU: 0 PID: 4406 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 : ipip_tunnel_xmit+0x2d4/0x430 net/ipv4/ipip.c:281
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 : ipip_tunnel_xmit+0x2d4/0x430 net/ipv4/ipip.c:281
sp : ffff8000a82673f0
x29: ffff8000a82673f0 x28: ffff00000fc24140 x27: ffff00006ab166ba
x26: 1fffe00001f8483e x25: dfff800000000000 x24: ffff00003b898080
x23: 0000000000000000 x22: 00000000fffffff6 x21: ffff00000fc241f4
x20: ffff00000fc24140 x19: ffff000046206000 x18: ffff800086d72d10
x17: 00000000008a008a x16: 008a4f8900000000 x15: 0000000000000001
x14: 1ffff00011028fbc x13: 0000000000000004 x12: 0000000000000001
x11: 0000000000040000 x10: 0000000000000f68 x9 : ffff80008d25a000
x8 : 0000000000000f69 x7 : ffff8000800477bc x6 : ffff8000800479b8
x5 : ffff0000687ca948 x4 : ffff8000a8267028 x3 : ffff800083f7f890
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]
 ipip_tunnel_xmit+0x2d4/0x430 net/ipv4/ipip.c:281
 __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@...glegroups.com>
Fixes: cb9f1b783850 ("ip: validate header length on virtual device xmit")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/ipv4/ipip.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index f2696eaadbe6..3f96364d65fd 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -278,11 +278,11 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb,
 	const struct iphdr  *tiph = &tunnel->parms.iph;
 	u8 ipproto;
 
-	if (!pskb_inet_may_pull(skb))
-		goto tx_error;
-
 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
+		if (!pskb_network_may_pull(skb, sizeof(struct iphdr)))
+			goto tx_error;
+
 		ipproto = IPPROTO_IPIP;
 		break;
 #if IS_ENABLED(CONFIG_MPLS)
-- 
2.30.2