[added to the 3.18 stable tree] vxlan: Fix double free of skb.

[Sasha Levin]

From: Pravin B Shelar <pshe...@nicira.com>

This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.

===============

[ Upstream commit 74f47278cb056ffe1d261df3e094d608c3569829 ]

In case of error vxlan_xmit_one() can free already freed skb.
Also fixes memory leak of dst-entry.

Fixes: acbf74a7630 ("vxlan: Refactor vxlan driver to make use
of the common UDP tunnel functions").

Signed-off-by: Pravin B Shelar <pshe...@nicira.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Sasha Levin <sasha.le...@oracle.com>
---
 drivers/net/vxlan.c | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index bcb1778..99da7ce 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1579,8 +1579,10 @@ static int vxlan6_xmit_skb(struct vxlan_sock *vs,
        bool udp_sum = !udp_get_no_check6_tx(vs->sock->sk);
 
        skb = udp_tunnel_handle_offloads(skb, udp_sum);
-       if (IS_ERR(skb))
-               return -EINVAL;
+       if (IS_ERR(skb)) {
+               err = -EINVAL;
+               goto err;
+       }
 
        skb_scrub_packet(skb, xnet);
 
@@ -1590,12 +1592,16 @@ static int vxlan6_xmit_skb(struct vxlan_sock *vs,
 
        /* Need space for new headers (invalidates iph ptr) */
        err = skb_cow_head(skb, min_headroom);
-       if (unlikely(err))
-               return err;
+       if (unlikely(err)) {
+               kfree_skb(skb);
+               goto err;
+       }
 
        skb = vlan_hwaccel_push_inside(skb);
-       if (WARN_ON(!skb))
-               return -ENOMEM;
+       if (WARN_ON(!skb)) {
+               err = -ENOMEM;
+               goto err;
+       }
 
        vxh = (struct vxlanhdr *) __skb_push(skb, sizeof(*vxh));
        vxh->vx_flags = htonl(VXLAN_FLAGS);
@@ -1606,6 +1612,9 @@ static int vxlan6_xmit_skb(struct vxlan_sock *vs,
        udp_tunnel6_xmit_skb(vs->sock, dst, skb, dev, saddr, daddr, prio,
                             ttl, src_port, dst_port);
        return 0;
+err:
+       dst_release(dst);
+       return err;
 }
 #endif
 
@@ -1621,7 +1630,7 @@ int vxlan_xmit_skb(struct vxlan_sock *vs,
 
        skb = udp_tunnel_handle_offloads(skb, udp_sum);
        if (IS_ERR(skb))
-               return -EINVAL;
+               return PTR_ERR(skb);
 
        min_headroom = LL_RESERVED_SPACE(rt->dst.dev) + rt->dst.header_len
                        + VXLAN_HLEN + sizeof(struct iphdr)
@@ -1629,8 +1638,10 @@ int vxlan_xmit_skb(struct vxlan_sock *vs,
 
        /* Need space for new headers (invalidates iph ptr) */
        err = skb_cow_head(skb, min_headroom);
-       if (unlikely(err))
+       if (unlikely(err)) {
+               kfree_skb(skb);
                return err;
+       }
 
        skb = vlan_hwaccel_push_inside(skb);
        if (WARN_ON(!skb))
@@ -1776,9 +1787,12 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct 
net_device *dev,
                                     tos, ttl, df, src_port, dst_port,
                                     htonl(vni << 8),
                                     !net_eq(vxlan->net, dev_net(vxlan->dev)));
-
-               if (err < 0)
+               if (err < 0) {
+                       /* skb is already freed. */
+                       skb = NULL;
                        goto rt_tx_error;
+               }
+
                iptunnel_xmit_stats(err, &dev->stats, dev->tstats);
 #if IS_ENABLED(CONFIG_IPV6)
        } else {
-- 
2.1.0

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