netfilter: nf_log: account for size of NLMSG_DONE attribute

We currently neither account for the nlattr size, nor do we consider
the size of the trailing NLMSG_DONE when allocating nlmsg skb.

This can result in nflog to stop working, as __nfulnl_send() re-tries
sending forever if it failed to append NLMSG_DONE (which will never
work if buffer is not large enough).

Reported-by: Houcheng Lin <houcheng@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index b1e3a0579416..8117fba8e661 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -649,7 +649,8 @@ nfulnl_log_packet(struct net *net,
                 + nla_total_size(sizeof(u_int32_t))     /* gid */
                 + nla_total_size(plen)                  /* prefix */
                 + nla_total_size(sizeof(struct nfulnl_msg_packet_hw))
-                + nla_total_size(sizeof(struct nfulnl_msg_packet_timestamp));
+                + nla_total_size(sizeof(struct nfulnl_msg_packet_timestamp))
+                + nla_total_size(sizeof(struct nfgenmsg));      /* NLMSG_DONE */
 
         if (in && skb_mac_header_was_set(skb)) {
                 size +=   nla_total_size(skb->dev->hard_header_len)
@@ -692,8 +693,7 @@ nfulnl_log_packet(struct net *net,
                 goto unlock_and_release;
         }
 
-        if (inst->skb &&
-            size > skb_tailroom(inst->skb) - sizeof(struct nfgenmsg)) {
+        if (inst->skb && size > skb_tailroom(inst->skb)) {
                 /* either the queue len is too high or we don't have
                  * enough room in the skb left. flush to userspace. */
                 __nfulnl_flush(inst);