re: af_mpls: fix undefined reference to ip6_route_output

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Roopa,

I have a concern about patch bf21563acc1d: "af_mpls: fix undefined
reference to ip6_route_output" from Jul 30, 2015.

net/mpls/af_mpls.c
   450  
   451          dev = find_outdev(net, cfg);
   452          if (IS_ERR(dev)) {

find_outdev() used to return NULL pointers but now it only returns NULL
if cfg->rc_via_table == NEIGH_LINK_TABLE or dev_get_by_index() fails.
I think it could lead to a NULL dereference and we don't check for that
here.

Returning a mix of error pointers and NULL is bad style, it needs a big
comment at the top of the function if it's deliberate.

   453                  err = PTR_ERR(dev);
   454                  dev = NULL;
   455                  goto errout;
   456          }

regards,
dan carpenter