netlink: add NLA_MIN_LEN

Rather than using NLA_UNSPEC for this type of thing, use NLA_MIN_LEN
so we can make NLA_UNSPEC be NLA_REJECT under certain conditions for
future attributes.

While at it, also use NLA_EXACT_LEN for the struct example.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/nlattr.c b/lib/nlattr.c
index d26de6156b97..465c9e8ef8a5 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -278,10 +278,17 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
                         }
                 }
                 break;
+
+        case NLA_UNSPEC:
+        case NLA_MIN_LEN:
+                if (attrlen < pt->len)
+                        goto out_err;
+                break;
+
         default:
                 if (pt->len)
                         minlen = pt->len;
-                else if (pt->type != NLA_UNSPEC)
+                else
                         minlen = nla_attr_minlen[pt->type];
 
                 if (attrlen < minlen)