[NETFILTER]: cleanup nfnetlink_check_attributes()

1) memset return parameter 'cda' (nfattr pointer array) only on success
2) a message without attributes and just a 'struct nfgenmsg' is valid,
   don't return -EINVAL
3) use likely() and unlikely() where apropriate

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 9 deletions

diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 578e4fe40945..84efffdbade3 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -163,17 +163,16 @@ nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
                         cb_id, subsys->cb_count);
                 return -EINVAL;
         }
-        
-        attr_count = subsys->cb[cb_id].attr_count;
-
-        memset(cda, 0, sizeof(struct nfattr *) * attr_count);
 
-        /* check attribute lengths. */
         min_len = NLMSG_ALIGN(sizeof(struct nfgenmsg));
-        if (nlh->nlmsg_len < min_len)
+        if (unlikely(nlh->nlmsg_len < min_len))
                 return -EINVAL;
 
-        if (nlh->nlmsg_len > min_len) {
+        attr_count = subsys->cb[cb_id].attr_count;
+        memset(cda, 0, sizeof(struct nfattr *) * attr_count);
+
+        /* check attribute lengths. */
+        if (likely(nlh->nlmsg_len > min_len)) {
                 struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
                 int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);
 
@@ -186,8 +185,10 @@ nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
                         }
                         attr = NFA_NEXT(attr, attrlen);
                 }
-        } else
-                return -EINVAL;
+        }
+
+        /* implicit: if nlmsg_len == min_len, we return 0, and an empty
+         * (zeroed) cda[] array. The message is valid, but empty. */
 
         return 0;
 }