netlink: fix NETLINK_RECV_NO_ENOBUFS in netlink_set_err()

Currently, ENOBUFS errors are reported to the socket via
netlink_set_err() even if NETLINK_RECV_NO_ENOBUFS is set. However,
that should not happen. This fixes this problem and it changes the
prototype of netlink_set_err() to return the number of sockets that
have set the NETLINK_RECV_NO_ENOBUFS socket option. This return
value is used in the next patch in these bugfix series.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 15 insertions, 4 deletions

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index fde27c017326..6eaca5e1e8ca 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -188,7 +188,7 @@ extern int netlink_has_listeners(struct sock *sk, unsigned int group);
 extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 pid, int nonblock);
 extern int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 pid,
                              __u32 group, gfp_t allocation);
-extern void netlink_set_err(struct sock *ssk, __u32 pid, __u32 group, int code);
+extern int netlink_set_err(struct sock *ssk, __u32 pid, __u32 group, int code);
 extern int netlink_register_notifier(struct notifier_block *nb);
 extern int netlink_unregister_notifier(struct notifier_block *nb);
 
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 320d0423a240..acbbae1e89b5 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1093,6 +1093,7 @@ static inline int do_one_set_err(struct sock *sk,
                                  struct netlink_set_err_data *p)
 {
         struct netlink_sock *nlk = nlk_sk(sk);
+        int ret = 0;
 
         if (sk == p->exclude_sk)
                 goto out;
@@ -1104,10 +1105,15 @@ static inline int do_one_set_err(struct sock *sk,
             !test_bit(p->group - 1, nlk->groups))
                 goto out;
 
+        if (p->code == ENOBUFS && nlk->flags & NETLINK_RECV_NO_ENOBUFS) {
+                ret = 1;
+                goto out;
+        }
+
         sk->sk_err = p->code;
         sk->sk_error_report(sk);
 out:
-        return 0;
+        return ret;
 }
 
 /**
@@ -1116,12 +1122,16 @@ out:
  * @pid: the PID of a process that we want to skip (if any)
  * @groups: the broadcast group that will notice the error
  * @code: error code, must be negative (as usual in kernelspace)
+ *
+ * This function returns the number of broadcast listeners that have set the
+ * NETLINK_RECV_NO_ENOBUFS socket option.
  */
-void netlink_set_err(struct sock *ssk, u32 pid, u32 group, int code)
+int netlink_set_err(struct sock *ssk, u32 pid, u32 group, int code)
 {
         struct netlink_set_err_data info;
         struct hlist_node *node;
         struct sock *sk;
+        int ret = 0;
 
         info.exclude_sk = ssk;
         info.pid = pid;
@@ -1132,9 +1142,10 @@ void netlink_set_err(struct sock *ssk, u32 pid, u32 group, int code)
         read_lock(&nl_table_lock);
 
         sk_for_each_bound(sk, node, &nl_table[ssk->sk_protocol].mc_list)
-                do_one_set_err(sk, &info);
+                ret += do_one_set_err(sk, &info);
 
         read_unlock(&nl_table_lock);
+        return ret;
 }
 EXPORT_SYMBOL(netlink_set_err);