netfilter: x_tables: suppress kmemcheck warning

Markus Trippelsdorf reports:

WARNING: kmemcheck: Caught 64-bit read from uninitialized memory (ffff88001e605480)
4055601e0088ffff000000000000000090686d81ffffffff0000000000000000
 u u u u u u u u u u u u u u u u i i i i i i i i u u u u u u u u
 ^
|RIP: 0010:[<ffffffff8166e561>]  [<ffffffff8166e561>] nf_register_net_hook+0x51/0x160
[..]
 [<ffffffff8166e561>] nf_register_net_hook+0x51/0x160
 [<ffffffff8166eaaf>] nf_register_net_hooks+0x3f/0xa0
 [<ffffffff816d6715>] ipt_register_table+0xe5/0x110
[..]

This warning is harmless; we copy 'uninitialized' data from the hook ops
but it will not be used.
Long term the structures keeping run-time data should be disentangled
from those only containing config-time data (such as where in the list
to insert a hook), but thats -next material.
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Suggested-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Aaron Conole <aconole@bytheb.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/x_tables.c

@@ -1513,7 +1513,7 @@ xt_hook_ops_alloc(const struct xt_table *table, nf_hookfn *fn)
 	if (!num_hooks)
 		return ERR_PTR(-EINVAL);
 
-	ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL);
+	ops = kcalloc(num_hooks, sizeof(*ops), GFP_KERNEL);
 	if (ops == NULL)
 		return ERR_PTR(-ENOMEM);