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Date:   Thu,  3 Jan 2019 21:43:34 +0100
From:   Stefano Brivio <sbrivio@...hat.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     syzbot <syzbot+4ad25edc7a33e4ab91e0@...kaller.appspotmail.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        syzkaller-bugs@...glegroups.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH net 1/2] fou: Prevent unbounded recursion in GUE error handler also with UDP-Lite

In commit 11789039da53 ("fou: Prevent unbounded recursion in GUE error
handler"), I didn't take care of the case where UDP-Lite is encapsulated
into UDP or UDP-Lite with GUE. From a syzbot report about a possibly
similar issue with GUE on IPv6, I just realised the same thing might
happen with a UDP-Lite inner payload.

Also skip exception handling for inner UDP-Lite protocol.

Fixes: 11789039da53 ("fou: Prevent unbounded recursion in GUE error handler")
Signed-off-by: Stefano Brivio <sbrivio@...hat.com>
---
 net/ipv4/fou.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index 0c9f171fb085..632863541082 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -1065,7 +1065,8 @@ static int gue_err(struct sk_buff *skb, u32 info)
 	 * recursion. Besides, this kind of encapsulation can't even be
 	 * configured currently. Discard this.
 	 */
-	if (guehdr->proto_ctype == IPPROTO_UDP)
+	if (guehdr->proto_ctype == IPPROTO_UDP ||
+	    guehdr->proto_ctype == IPPROTO_UDPLITE)
 		return -EOPNOTSUPP;
 
 	skb_set_transport_header(skb, -(int)sizeof(struct icmphdr));
-- 
2.20.1

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