netdev - [PATCH net 4/4] udp: fix possible user after free in error handler

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Message-Id: <d061aeb3865d3deee25ca339ea1115e1150317d8.1550767274.git.pabeni@redhat.com>
Date:   Thu, 21 Feb 2019 17:44:00 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Stefano Brivio <sbrivio@...hat.com>
Subject: [PATCH net 4/4] udp: fix possible user after free in error handler

Similar to the previous commit, this addresses the same issue for
ipv4: use a single fetch operation and use the correct rcu
annotation.

Fixes: e7cc082455cb ("udp: Support for error handlers of tunnels with arbitrary destination port")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Acked-by: Stefano Brivio <sbrivio@...hat.com>
---
 net/ipv4/udp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 5c3cd5d84a6f..372fdc5381a9 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -562,10 +562,12 @@ static int __udp4_lib_err_encap_no_sk(struct sk_buff *skb, u32 info)
 
 	for (i = 0; i < MAX_IPTUN_ENCAP_OPS; i++) {
 		int (*handler)(struct sk_buff *skb, u32 info);
+		const struct ip_tunnel_encap_ops *encap;
 
-		if (!iptun_encaps[i])
+		encap = rcu_dereference(iptun_encaps[i]);
+		if (!encap)
 			continue;
-		handler = rcu_dereference(iptun_encaps[i]->err_handler);
+		handler = encap->err_handler;
 		if (handler && !handler(skb, info))
 			return 0;
 	}
-- 
2.20.1