From: Neil Horman <nhorman@redhat.com>
Date: Wed, 13 Feb 2008 15:31:20 -0500
Subject: [net] sctp: socket initialization race
Message-id: 20080213203120.GA30902@hmsendeavour.rdu.redhat.com
O-Subject: [RHEL 5.2 PATCH] corrected fix for sctp oops under load (bz 426234)
Bugzilla: 426234

We recently discovered that bz 426234, which had a patch posted for it, didn't
actually fix the problem.  While the patch that was posted is good to have in
place, a bit more research showed that the actuall problem was a race in module
initialization under heavy use.  Sctp registers itself as an available protocol
with the inet layer first in its module init routine, so its possible that a
user space app can try to create an sctp socket before the module is done
initalizing.  This patch is a backport of upstream commit
827bf12236fbafc02bc899aec1b37c342c8cf4e5, and closes the race, by moving the
protocol registration to the end of the init routine, giving the module the
ability to initalize first.

Tested by Abhijith Das up in the Minneapolis office with successful results.

Regards
Neil

Acked-by: "David S. Miller" <davem@redhat.com>
Acked-by: Thomas Graf <tgraf@redhat.com>

diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index beaac12..b3f06d3 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -323,11 +323,15 @@ static inline int sctp_sysctl_jiffies_ms(ctl_table *table, int __user *name, int
 
 int sctp_v6_init(void);
 void sctp_v6_exit(void);
+int sctp_v6_add_protocol(void);
+void sctp_v6_del_protocol(void);
 
 #else /* #ifdef defined(CONFIG_IPV6) */
 
 static inline int sctp_v6_init(void) { return 0; }
 static inline void sctp_v6_exit(void) { return; }
+static inline int sctp_v6_add_protocol(void) { return 0; }
+static inline void sctp_v6_del_protocol(void) { return; }
 
 #endif /* #if defined(CONFIG_IPV6) */
 
diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
index c77deb4..009fa02 100644
--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -962,45 +962,52 @@ static struct sctp_pf sctp_pf_inet6_specific = {
 	.af            = &sctp_ipv6_specific,
 };
 
-/* Initialize IPv6 support and register with inet6 stack.  */
+/* Initialize IPv6 support and register with socket layer.  */
 int sctp_v6_init(void)
 {
-	int rc = proto_register(&sctpv6_prot, 1);
+	int rc;
 
+	/* Register the SCTP specific PF_INET6 functions. */
+	sctp_register_pf(&sctp_pf_inet6_specific, PF_INET6);
+
+	/* Register the SCTP specific AF_INET6 functions. */
+	sctp_register_af(&sctp_ipv6_specific);
+
+	rc = proto_register(&sctpv6_prot, 1);
 	if (rc)
-		goto out;
-	/* Register inet6 protocol. */
-	rc = -EAGAIN;
-	if (inet6_add_protocol(&sctpv6_protocol, IPPROTO_SCTP) < 0)
-		goto out_unregister_sctp_proto;
+		return rc;
 
 	/* Add SCTPv6(UDP and TCP style) to inetsw6 linked list. */
 	inet6_register_protosw(&sctpv6_seqpacket_protosw);
 	inet6_register_protosw(&sctpv6_stream_protosw);
 
-	/* Register the SCTP specific PF_INET6 functions. */
-	sctp_register_pf(&sctp_pf_inet6_specific, PF_INET6);
-
-	/* Register the SCTP specific AF_INET6 functions. */
-	sctp_register_af(&sctp_ipv6_specific);
+	return 0;
+}
 
+/* Register with inet6 layer. */
+int sctp_v6_add_protocol(void)
+{
 	/* Register notifier for inet6 address additions/deletions. */
 	register_inet6addr_notifier(&sctp_inet6addr_notifier);
-	rc = 0;
-out:
-	return rc;
-out_unregister_sctp_proto:
-	proto_unregister(&sctpv6_prot);
-	goto out;
+
+	if (inet6_add_protocol(&sctpv6_protocol, IPPROTO_SCTP) < 0)
+		return -EAGAIN;
+
+	return 0;
 }
 
 /* IPv6 specific exit support. */
 void sctp_v6_exit(void)
 {
-	list_del(&sctp_ipv6_specific.list);
-	inet6_del_protocol(&sctpv6_protocol, IPPROTO_SCTP);
 	inet6_unregister_protosw(&sctpv6_seqpacket_protosw);
 	inet6_unregister_protosw(&sctpv6_stream_protosw);
-	unregister_inet6addr_notifier(&sctp_inet6addr_notifier);
 	proto_unregister(&sctpv6_prot);
+	list_del(&sctp_ipv6_specific.list);
+}
+
+/* Unregister with inet6 layer. */
+void sctp_v6_del_protocol(void)
+{
+	inet6_del_protocol(&sctpv6_protocol, IPPROTO_SCTP);
+	unregister_inet6addr_notifier(&sctp_inet6addr_notifier);
 }
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 43ccaf9..f4ff4e4 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -995,28 +995,14 @@ SCTP_STATIC __init int sctp_init(void)
 	if (!sctp_sanity_check())
 		goto out;
 
-	status = proto_register(&sctp_prot, 1);
-	if (status)
-		goto out;
-
-	/* Add SCTP to inet_protos hash table.  */
-	status = -EAGAIN;
-	if (inet_add_protocol(&sctp_protocol, IPPROTO_SCTP) < 0)
-		goto err_add_protocol;
-
-	/* Add SCTP(TCP and UDP style) to inetsw linked list.  */
-	inet_register_protosw(&sctp_seqpacket_protosw);
-	inet_register_protosw(&sctp_stream_protosw);
-
-	/* Allocate a cache pools. */
+	/* Allocate bind_bucket and chunk caches. */
 	status = -ENOBUFS;
 	sctp_bucket_cachep = kmem_cache_create("sctp_bind_bucket",
 					       sizeof(struct sctp_bind_bucket),
 					       0, SLAB_HWCACHE_ALIGN,
 					       NULL, NULL);
-
 	if (!sctp_bucket_cachep)
-		goto err_bucket_cachep;
+		goto out;
 
 	sctp_chunk_cachep = kmem_cache_create("sctp_chunk",
 					       sizeof(struct sctp_chunk),
@@ -1195,6 +1181,14 @@ SCTP_STATIC __init int sctp_init(void)
 	INIT_LIST_HEAD(&sctp_address_families);
 	sctp_register_af(&sctp_ipv4_specific);
 
+	status = proto_register(&sctp_prot, 1);
+	if (status)
+		goto err_proto_register;
+
+	/* Register SCTP(UDP and TCP style) with socket layer.  */
+	inet_register_protosw(&sctp_seqpacket_protosw);
+	inet_register_protosw(&sctp_stream_protosw);
+
 	status = sctp_v6_init();
 	if (status)
 		goto err_v6_init;
@@ -1213,15 +1207,37 @@ SCTP_STATIC __init int sctp_init(void)
 	/* Register notifier for inet address additions/deletions. */
 	register_inetaddr_notifier(&sctp_inetaddr_notifier);
 
+	/* Register SCTP with inet layer.  */
+	if (inet_add_protocol(&sctp_protocol, IPPROTO_SCTP) < 0) {
+		status = -EAGAIN;
+		goto err_add_protocol;
+	}
+ 
+	/* Register SCTP with inet6 layer.  */
+	status = sctp_v6_add_protocol();
+	if (status)
+		goto err_v6_add_protocol;
+
+
 	sctp_get_local_addr_list();
 
 	__unsafe(THIS_MODULE);
 	status = 0;
 out:
 	return status;
+err_v6_add_protocol:
+	inet_del_protocol(&sctp_protocol, IPPROTO_SCTP);
+	unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
+err_add_protocol:
+	sctp_free_local_addr_list();
+	sock_release(sctp_ctl_socket);
 err_ctl_sock_init:
 	sctp_v6_exit();
 err_v6_init:
+	inet_unregister_protosw(&sctp_stream_protosw);
+	inet_unregister_protosw(&sctp_seqpacket_protosw);
+	proto_unregister(&sctp_prot);
+err_proto_register:
 	sctp_sysctl_unregister();
 	list_del(&sctp_ipv4_specific.list);
 	free_pages((unsigned long)sctp_port_hashtable,
@@ -1235,19 +1251,13 @@ err_ehash_alloc:
 			     sizeof(struct sctp_hashbucket)));
 err_ahash_alloc:
 	sctp_dbg_objcnt_exit();
-err_init_proc:
 	sctp_proc_exit();
+err_init_proc:
 	cleanup_sctp_mibs();
 err_init_mibs:
 	kmem_cache_destroy(sctp_chunk_cachep);
 err_chunk_cachep:
 	kmem_cache_destroy(sctp_bucket_cachep);
-err_bucket_cachep:
-	inet_del_protocol(&sctp_protocol, IPPROTO_SCTP);
-	inet_unregister_protosw(&sctp_seqpacket_protosw);
-	inet_unregister_protosw(&sctp_stream_protosw);
-err_add_protocol:
-	proto_unregister(&sctp_prot);
 	goto out;
 }
 
@@ -1258,8 +1268,9 @@ SCTP_STATIC __exit void sctp_exit(void)
 	 * up all the remaining associations and all that memory.
 	 */
 
-	/* Unregister notifier for inet address additions/deletions. */
-	unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
+	/* Unregister with inet6/inet layers. */
+	sctp_v6_del_protocol();
+	inet_del_protocol(&sctp_protocol, IPPROTO_SCTP);
 
 	/* Free the local address list.  */
 	sctp_free_local_addr_list();
@@ -1267,7 +1278,16 @@ SCTP_STATIC __exit void sctp_exit(void)
 	/* Free the control endpoint.  */
 	sock_release(sctp_ctl_socket);
 
+	/* Cleanup v6 initializations. */
 	sctp_v6_exit();
+
+	/* Unregister with socket layer. */
+	inet_unregister_protosw(&sctp_stream_protosw);
+	inet_unregister_protosw(&sctp_seqpacket_protosw);
+
+	/* Unregister notifier for inet address additions/deletions. */
+	unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
+
 	sctp_sysctl_unregister();
 	list_del(&sctp_ipv4_specific.list);
 
@@ -1279,16 +1299,13 @@ SCTP_STATIC __exit void sctp_exit(void)
 		   get_order(sctp_port_hashsize *
 			     sizeof(struct sctp_bind_hashbucket)));
 
-	kmem_cache_destroy(sctp_chunk_cachep);
-	kmem_cache_destroy(sctp_bucket_cachep);
-
 	sctp_dbg_objcnt_exit();
 	sctp_proc_exit();
 	cleanup_sctp_mibs();
 
-	inet_del_protocol(&sctp_protocol, IPPROTO_SCTP);
-	inet_unregister_protosw(&sctp_seqpacket_protosw);
-	inet_unregister_protosw(&sctp_stream_protosw);
+	kmem_cache_destroy(sctp_chunk_cachep);
+	kmem_cache_destroy(sctp_bucket_cachep);
+
 	proto_unregister(&sctp_prot);
 }