ipcomp: Avoid duplicate calls to ipcomp_destroy

When ipcomp_tunnel_attach fails we will call ipcomp_destroy twice.
This may lead to double-frees on certain structures.

As there is no reason to explicitly call ipcomp_destroy, this patch
removes it from ipcomp*.c and lets the standard xfrm_state destruction
take place.

This is based on the discovery and patch by Alexey Dobriyan.
Tested-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ipcomp.c

@@ -124,16 +124,12 @@ static int ipcomp4_init_state(struct xfrm_state *x)
 	if (x->props.mode == XFRM_MODE_TUNNEL) {
 		err = ipcomp_tunnel_attach(x);
 		if (err)
-			goto error_tunnel;
+			goto out;
 	}
 
 	err = 0;
 out:
 	return err;
-
-error_tunnel:
-	ipcomp_destroy(x);
-	goto out;
 }
 
 static const struct xfrm_type ipcomp_type = {

net/ipv6/ipcomp6.c

@@ -154,16 +154,12 @@ static int ipcomp6_init_state(struct xfrm_state *x)
 	if (x->props.mode == XFRM_MODE_TUNNEL) {
 		err = ipcomp6_tunnel_attach(x);
 		if (err)
-			goto error_tunnel;
+			goto out;
 	}
 
 	err = 0;
 out:
 	return err;
-error_tunnel:
-	ipcomp_destroy(x);
-
-	goto out;
 }
 
 static const struct xfrm_type ipcomp6_type =