Use thr_once() with once_t controls to initialize various thread_key_t

objects used to provide per-thread storage in the RPC code.  Almost all
of these used double-checking with a dedicated mutex (tsd_lock) to do this
before.  However, that is not always safe with more relaxed memory orders.
There were also other bugs, such as one in __rpc_createrr() that caused a
new key to be allocated each time __rpc_createrr() was invoked.

PR:		threads/144558
Reported by:	Sam Robb  samrobb of averesystems com (key leak)
MFC after:	1 week

1 files changed, 15 insertions, 12 deletions

diff --git a/lib/libc/rpc/rpc_generic.c b/lib/libc/rpc/rpc_generic.c
index 81bd92b..1bd7e15 100644
--- a/lib/libc/rpc/rpc_generic.c
+++ b/lib/libc/rpc/rpc_generic.c
@@ -221,6 +221,18 @@ getnettype(nettype)
 	return (_rpctypelist[i].type);
 }
 
+static thread_key_t tcp_key, udp_key;
+static once_t keys_once = ONCE_INITIALIZER;
+static int tcp_key_error, udp_key_error;
+
+static void
+keys_init(void)
+{
+
+	tcp_key_error = thr_keycreate(&tcp_key, free);
+	udp_key_error = thr_keycreate(&udp_key, free);
+}
+
 /*
  * For the given nettype (tcp or udp only), return the first structure found.
  * This should be freed by calling freenetconfigent()
@@ -242,19 +254,10 @@ __rpc_getconfip(nettype)
 		netid_udp = netid_udp_main;
 		netid_tcp = netid_tcp_main;
 	} else {
-		if (tcp_key == 0) {
-			mutex_lock(&tsd_lock);
-			if (tcp_key == 0)
-				thr_keycreate(&tcp_key, free);
-			mutex_unlock(&tsd_lock);
-		}
+		if (thr_once(&keys_once, keys_init) != 0 ||
+		    tcp_key_error != 0 || udp_key_error != 0)
+			return (NULL);
 		netid_tcp = (char *)thr_getspecific(tcp_key);
-		if (udp_key == 0) {
-			mutex_lock(&tsd_lock);
-			if (udp_key == 0)
-				thr_keycreate(&udp_key, free);
-			mutex_unlock(&tsd_lock);
-		}
 		netid_udp = (char *)thr_getspecific(udp_key);
 	}
 	if (!netid_udp && !netid_tcp) {