Coverity says:

*** CID 1338065:  Error handling issues  (CHECKED_RETURN)
/net/tipc/udp_media.c: 162 in tipc_udp_send_msg()
156             struct udp_media_addr *dst = (struct udp_media_addr 
*)&dest->value;
157             struct udp_media_addr *src = (struct udp_media_addr 
*)&b->addr.value;
158             struct sk_buff *clone;
159             struct rtable *rt;
160
161             if (skb_headroom(skb) < UDP_MIN_HEADROOM)
>>>     CID 1338065:  Error handling issues  (CHECKED_RETURN)
>>>     Calling "pskb_expand_head" without checking return value (as is done 
>>> elsewhere 51 out of 56 times).
162                     pskb_expand_head(skb, UDP_MIN_HEADROOM, 0, GFP_ATOMIC);
163
164             clone = skb_clone(skb, GFP_ATOMIC);
165             skb_set_inner_protocol(clone, htons(ETH_P_TIPC));
166             ub = rcu_dereference_rtnl(b->media_ptr);
167             if (!ub) {

When expanding buffer headroom over udp tunnel with pskb_expand_head(),
it's unfortunate that we don't check its return value. As a result, if
the function returns an error code due to the lack of memory, it may
cause unpredictable consequence as we unconditionally consider that
it's always successful.

Fixes: e53567948f82 ("tipc: conditionally expand buffer headroom over udp 
tunnel")
Reported-by: <scan-ad...@coverity.com>
Cc: Stephen Hemminger <step...@networkplumber.org>
Signed-off-by: Ying Xue <ying....@windriver.com>
---
v2:
 * When pskb_expand_head() returns negative error codes instead of zero used
   in original version, we should jump to exception branch, pointed out by
   David.

 net/tipc/udp_media.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c
index ad2719a..70c0327 100644
--- a/net/tipc/udp_media.c
+++ b/net/tipc/udp_media.c
@@ -158,8 +158,11 @@ static int tipc_udp_send_msg(struct net *net, struct 
sk_buff *skb,
        struct udp_media_addr *src = (struct udp_media_addr *)&b->addr.value;
        struct rtable *rt;
 
-       if (skb_headroom(skb) < UDP_MIN_HEADROOM)
-               pskb_expand_head(skb, UDP_MIN_HEADROOM, 0, GFP_ATOMIC);
+       if (skb_headroom(skb) < UDP_MIN_HEADROOM) {
+               err = pskb_expand_head(skb, UDP_MIN_HEADROOM, 0, GFP_ATOMIC);
+               if (err)
+                       goto tx_error;
+       }
 
        skb_set_inner_protocol(skb, htons(ETH_P_TIPC));
        ub = rcu_dereference_rtnl(b->media_ptr);
-- 
1.7.9.5

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