xfrm: fix a NULL-ptr deref in xfrm_local_error
This patch is to fix a crash:
[ ] kasan: GPF could be caused by NULL-ptr deref or user memory access
[ ] general protection fault: 0000 [#1] SMP KASAN PTI
[ ] RIP: 0010:ipv6_local_error+0xac/0x7a0
[ ] Call Trace:
[ ] xfrm6_local_error+0x1eb/0x300
[ ] xfrm_local_error+0x95/0x130
[ ] __xfrm6_output+0x65f/0xb50
[ ] xfrm6_output+0x106/0x46f
[ ] udp_tunnel6_xmit_skb+0x618/0xbf0 [ip6_udp_tunnel]
[ ] vxlan_xmit_one+0xbc6/0x2c60 [vxlan]
[ ] vxlan_xmit+0x6a0/0x4276 [vxlan]
[ ] dev_hard_start_xmit+0x165/0x820
[ ] __dev_queue_xmit+0x1ff0/0x2b90
[ ] ip_finish_output2+0xd3e/0x1480
[ ] ip_do_fragment+0x182d/0x2210
[ ] ip_output+0x1d0/0x510
[ ] ip_send_skb+0x37/0xa0
[ ] raw_sendmsg+0x1b4c/0x2b80
[ ] sock_sendmsg+0xc0/0x110
This occurred when sending a v4 skb over vxlan6 over ipsec, in which case
skb->protocol == htons(ETH_P_IPV6) while skb->sk->sk_family == AF_INET in
xfrm_local_error(). Then it will go to xfrm6_local_error() where it tries
to get ipv6 info from a ipv4 sk.
This issue was actually fixed by Commit 628e341f319f ("xfrm: make local
error reporting more robust"), but brought back by Commit 844d48746e4b
("xfrm: choose protocol family by skb protocol").
So to fix it, we should call xfrm6_local_error() only when skb->protocol
is htons(ETH_P_IPV6) and skb->sk->sk_family is AF_INET6.
Fixes: 844d48746e4b ("xfrm: choose protocol family by skb protocol")
Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
index 69c33ca..69c4900 100644
--- a/net/xfrm/xfrm_output.c
+++ b/net/xfrm/xfrm_output.c
@@ -642,7 +642,8 @@ void xfrm_local_error(struct sk_buff *skb, int mtu)
if (skb->protocol == htons(ETH_P_IP))
proto = AF_INET;
- else if (skb->protocol == htons(ETH_P_IPV6))
+ else if (skb->protocol == htons(ETH_P_IPV6) &&
+ skb->sk->sk_family == AF_INET6)
proto = AF_INET6;
else
return;