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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jianlin Shi <jishi@redhat.com>,
        Alexey Kodanev <alexey.kodanev@oracle.com>,
        Hangbin Liu <liuhangbin@gmail.com>,
        Stefano Brivio <sbrivio@redhat.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.20 138/183] geneve: should not call rt6_lookup() when ipv6 was disabled
Date:   Mon, 25 Feb 2019 22:11:51 +0100
Message-Id: <20190225195118.166886226@linuxfoundation.org>
In-Reply-To: <20190225195054.748060397@linuxfoundation.org>
References: <20190225195054.748060397@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

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

From: Hangbin Liu <liuhangbin@gmail.com>

[ Upstream commit c0a47e44c0980b3b23ee31fa7936d70ea5dce491 ]

When we add a new GENEVE device with IPv6 remote, checking only for
IS_ENABLED(CONFIG_IPV6) is not enough as we may disable IPv6 in the
kernel command line (ipv6.disable=1), and calling rt6_lookup() would
cause a NULL pointer dereference.

v2:
- don't mix declarations and code (reported by Stefano Brivio, Eric Dumazet)
- there's no need to use in6_dev_get() as we only need to check that
  idev exists (reported by David Ahern). This is under RTNL, so we can
  simply use __in6_dev_get() instead (Stefano, Eric).

Reported-by: Jianlin Shi <jishi@redhat.com>
Fixes: c40e89fd358e9 ("geneve: configure MTU based on a lower device")
Cc: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/geneve.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -1426,9 +1426,13 @@ static void geneve_link_config(struct ne
 	}
 #if IS_ENABLED(CONFIG_IPV6)
 	case AF_INET6: {
-		struct rt6_info *rt = rt6_lookup(geneve->net,
-						 &info->key.u.ipv6.dst, NULL, 0,
-						 NULL, 0);
+		struct rt6_info *rt;
+
+		if (!__in6_dev_get(dev))
+			break;
+
+		rt = rt6_lookup(geneve->net, &info->key.u.ipv6.dst, NULL, 0,
+				NULL, 0);
 
 		if (rt && rt->dst.dev)
 			ldev_mtu = rt->dst.dev->mtu - GENEVE_IPV6_HLEN;