net: ipv6: fix error return code

Initialize return variable before exiting on an error path.

The initial initialization of the return variable is also dropped, because
that value is never used.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
(
if@p1 (\(ret < 0\|ret != 0\))
 { ... return ret; }
|
ret@p1 = 0
)
... when != ret = e1
    when != &ret
*if(...)
{
  ... when != ret = e2
      when forall
 return ret;
}

// </smpl>
Signed-off-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/esp6.c

@@ -167,8 +167,6 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 	struct esp_data *esp = x->data;
 
 	/* skb is pure payload to encrypt */
-	err = -ENOMEM;
-
 	aead = esp->aead;
 	alen = crypto_aead_authsize(aead);
 
@@ -203,8 +201,10 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 	}
 
 	tmp = esp_alloc_tmp(aead, nfrags + sglists, seqhilen);
-	if (!tmp)
+	if (!tmp) {
+		err = -ENOMEM;
 		goto error;
+	}
 
 	seqhi = esp_tmp_seqhi(tmp);
 	iv = esp_tmp_iv(aead, tmp, seqhilen);