netfilter: x_tables: assert minimum target size

commit a08e4e190b866579896c09af59b3bdca821da2cd upstream.

The target size includes the size of the xt_entry_target struct.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Florian Westphal

net/netfilter/x_tables.c

@@ -567,6 +567,9 @@ int xt_check_entry_offsets(const void *base,
 		return -EINVAL;
 
 	t = (void *)(e + target_offset);
+	if (t->u.target_size < sizeof(*t))
+		return -EINVAL;
+
 	if (target_offset + t->u.target_size > next_offset)
 		return -EINVAL;