netfilter: nf_log: release skbuff on nlmsg put failure

commit b51d3fa364885a2c1e1668f88776c67c95291820 upstream.

The kernel should reserve enough room in the skb so that the DONE
message can always be appended.  However, in case of e.g. new attribute
erronously not being size-accounted for, __nfulnl_send() will still
try to put next nlmsg into this full skbuf, causing the skb to be stuck
forever and blocking delivery of further messages.

Fix issue by releasing skb immediately after nlmsg_put error and
WARN() so we can track down the cause of such size mismatch.

[ fw@strlen.de: add tailroom/len info to WARN ]

Signed-off-by: Houcheng Lin <houcheng@gmail.com>
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>

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 3d66b83a5c88d80cbb3df5780de4aa00919bf635..216261dd32aeca3f9ec9b7027484e7f2bcabeba1 100644 (file)
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -348,26 +348,25 @@ nfulnl_alloc_skb(u32 peer_portid, unsigned int inst_size, unsigned int pkt_size)
        return skb;
 }
 
-static int
+static void
 __nfulnl_send(struct nfulnl_instance *inst)
 {
-       int status = -1;
-
        if (inst->qlen > 1) {
                struct nlmsghdr *nlh = nlmsg_put(inst->skb, 0, 0,
                                                 NLMSG_DONE,
                                                 sizeof(struct nfgenmsg),
                                                 0);
-               if (!nlh)
+               if (WARN_ONCE(!nlh, "bad nlskb size: %u, tailroom %d\n",
+                             inst->skb->len, skb_tailroom(inst->skb))) {
+                       kfree_skb(inst->skb);
                        goto out;
+               }
        }
-       status = nfnetlink_unicast(inst->skb, inst->net, inst->peer_portid,
-                                  MSG_DONTWAIT);
-
+       nfnetlink_unicast(inst->skb, inst->net, inst->peer_portid,
+                         MSG_DONTWAIT);
+out:
        inst->qlen = 0;
        inst->skb = NULL;
-out:
-       return status;
 }
 
 static void