netfilter: nft_compat: use call_rcu for nfnl_compat_get

Just use .call_rcu instead.  We can drop the rcu read lock
after obtaining a reference and re-acquire on return.

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

diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c
index 1d99a1e..8d1ff65 100644 (file)
--- a/net/netfilter/nft_compat.c
+++ b/net/netfilter/nft_compat.c
@@ -611,10 +611,10 @@ nla_put_failure:
        return -1;
 }
 
-static int nfnl_compat_get(struct net *net, struct sock *nfnl,
-                          struct sk_buff *skb, const struct nlmsghdr *nlh,
-                          const struct nlattr * const tb[],
-                          struct netlink_ext_ack *extack)
+static int nfnl_compat_get_rcu(struct net *net, struct sock *nfnl,
+                              struct sk_buff *skb, const struct nlmsghdr *nlh,
+                              const struct nlattr * const tb[],
+                              struct netlink_ext_ack *extack)
 {
        int ret = 0, target;
        struct nfgenmsg *nfmsg;
@@ -653,16 +653,21 @@ static int nfnl_compat_get(struct net *net, struct sock *nfnl,
                return -EINVAL;
        }
 
+       if (!try_module_get(THIS_MODULE))
+               return -EINVAL;
+
+       rcu_read_unlock();
        try_then_request_module(xt_find_revision(nfmsg->nfgen_family, name,
                                                 rev, target, &ret),
                                                 fmt, name);
-
        if (ret < 0)
-               return ret;
+               goto out_put;
 
        skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
-       if (skb2 == NULL)
-               return -ENOMEM;
+       if (skb2 == NULL) {
+               ret = -ENOMEM;
+               goto out_put;
+       }
 
        /* include the best revision for this extension in the message */
        if (nfnl_compat_fill_info(skb2, NETLINK_CB(skb).portid,
@@ -672,14 +677,16 @@ static int nfnl_compat_get(struct net *net, struct sock *nfnl,
                                  nfmsg->nfgen_family,
                                  name, ret, target) <= 0) {
                kfree_skb(skb2);
-               return -ENOSPC;
+               goto out_put;
        }
 
        ret = netlink_unicast(nfnl, skb2, NETLINK_CB(skb).portid,
                                MSG_DONTWAIT);
        if (ret > 0)
                ret = 0;
-
+out_put:
+       rcu_read_lock();
+       module_put(THIS_MODULE);
        return ret == -EAGAIN ? -ENOBUFS : ret;
 }
 
@@ -691,7 +698,7 @@ static const struct nla_policy nfnl_compat_policy_get[NFTA_COMPAT_MAX+1] = {
 };
 
 static const struct nfnl_callback nfnl_nft_compat_cb[NFNL_MSG_COMPAT_MAX] = {
-       [NFNL_MSG_COMPAT_GET]           = { .call = nfnl_compat_get,
+       [NFNL_MSG_COMPAT_GET]           = { .call_rcu = nfnl_compat_get_rcu,
                                            .attr_count = NFTA_COMPAT_MAX,
                                            .policy = nfnl_compat_policy_get },
 };