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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, Guillaume Nault <gnault@redhat.com>,
        Stefano Brivio <sbrivio@redhat.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 5.1 17/98] vxlan: Dont assume linear buffers in error handler
Date:   Thu, 20 Jun 2019 19:56:44 +0200
Message-Id: <20190620174350.058456278@linuxfoundation.org>
In-Reply-To: <20190620174349.443386789@linuxfoundation.org>
References: <20190620174349.443386789@linuxfoundation.org>
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From: Stefano Brivio <sbrivio@redhat.com>

[ Upstream commit 8399a6930d12f5965230f4ff058228a4cc80c0b9 ]

In commit c3a43b9fec8a ("vxlan: ICMP error lookup handler") I wrongly
assumed buffers from icmp_socket_deliver() would be linear. This is not
the case: icmp_socket_deliver() only guarantees we have 8 bytes of linear
data.

Eric fixed this same issue for fou and fou6 in commits 26fc181e6cac
("fou, fou6: do not assume linear skbs") and 5355ed6388e2 ("fou, fou6:
avoid uninit-value in gue_err() and gue6_err()").

Use pskb_may_pull() instead of checking skb->len, and take into account
the fact we later access the VXLAN header with udp_hdr(), so we also
need to sum skb_transport_header() here.

Reported-by: Guillaume Nault <gnault@redhat.com>
Fixes: c3a43b9fec8a ("vxlan: ICMP error lookup handler")
Signed-off-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/vxlan.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1765,7 +1765,7 @@ static int vxlan_err_lookup(struct sock
 	struct vxlanhdr *hdr;
 	__be32 vni;
 
-	if (skb->len < VXLAN_HLEN)
+	if (!pskb_may_pull(skb, skb_transport_offset(skb) + VXLAN_HLEN))
 		return -EINVAL;
 
 	hdr = vxlan_hdr(skb);