linux-kernel - [PATCH 3.2 1/4] ipv4: keep skb->dst around in presence of IP options

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Message-ID: <lsq.1491052673.430543076@decadent.org.uk>
Date:   Sat, 01 Apr 2017 14:17:53 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Eric Dumazet" <edumazet@...gle.com>,
        "Anarcheuz Fritz" <anarcheuz@...il.com>
Subject: [PATCH 3.2 1/4] ipv4: keep skb->dst around in presence of IP  options

3.2.88-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>

Upstream commit 34b2cef20f19c87999fff3da4071e66937db9644
("ipv4: keep skb->dst around in presence of IP options") incorrectly
root caused commit d826eb14ecef ("ipv4: PKTINFO doesnt need dst
reference") as bug origin.

This patch should fix the issue for 3.2.xx stable kernels, since IPv4
options seem to get more traction these days, after years of oblivion ;)

Fixes: f84af32cbca70 ("net: ip_queue_rcv_skb() helper"))
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Anarcheuz Fritz <anarcheuz@...il.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1009,7 +1009,8 @@ e_inval:
  */
 int ip_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
-	if (!(inet_sk(sk)->cmsg_flags & IP_CMSG_PKTINFO))
+	if (!(inet_sk(sk)->cmsg_flags & IP_CMSG_PKTINFO) &&
+	    !IPCB(skb)->opt.optlen)
 		skb_dst_drop(skb);
 	return sock_queue_rcv_skb(sk, skb);
 }