[PATCH net v2 1/2] sctp: avoid auth_enable sysctl UAF during netns teardown

[PATCH net v2 1/2] sctp: avoid auth_enable sysctl UAF during netns teardown

[Ren Wei]

From: Zhiling Zou <roxy520tt@gmail.com>

proc_sctp_do_auth() updates the SCTP control socket after changing
net.sctp.auth_enable. The handler gets the per-net SCTP state from
ctl->data, so an already opened sysctl file can still target a network
namespace while that namespace is being torn down.

SCTP previously registered its per-net sysctls from sctp_defaults_init(),
while the control socket is created later from sctp_ctrlsock_init(). This
exposed a window during initialization where auth_enable was writable
before net->sctp.ctl_sock existed, and a teardown window where auth_enable
stayed writable after inet_ctl_sock_destroy() had released the control
socket.

Move the per-net SCTP sysctl registration into sctp_ctrlsock_init() after
sctp_ctl_sock_init() succeeds, and unregister the sysctl table before
destroying the control socket in sctp_ctrlsock_exit(). If sysctl
registration fails after the control socket was created, destroy the
control socket in the same init path.

Make sctp_sysctl_net_unregister() tolerate a missing header and clear the
saved pointer so init-error and exit paths can safely share the unregister
helper.

Fixes: 15649fd5415e ("sctp: sysctl: auth_enable: avoid using current->nsproxy")
Cc: stable@vger.kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Co-developed-by: Qi Tang <tpluszz77@gmail.com>
Signed-off-by: Qi Tang <tpluszz77@gmail.com>
Signed-off-by: Zhiling Zou <roxy520tt@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
---
 net/sctp/protocol.c | 17 ++++++++++-------
 net/sctp/sysctl.c   |  9 +++++++--
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 587b0017a67d..f5fe6ddf0d7d 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1382,10 +1382,6 @@ static int __net_init sctp_defaults_init(struct net *net)
 	net->sctp.l3mdev_accept = 1;
 #endif
 
-	status = sctp_sysctl_net_register(net);
-	if (status)
-		goto err_sysctl_register;
-
 	/* Allocate and initialise sctp mibs.  */
 	status = init_sctp_mibs(net);
 	if (status)
@@ -1419,8 +1415,6 @@ static int __net_init sctp_defaults_init(struct net *net)
 	cleanup_sctp_mibs(net);
 #endif
 err_init_mibs:
-	sctp_sysctl_net_unregister(net);
-err_sysctl_register:
 	return status;
 }
 
@@ -1435,7 +1429,6 @@ static void __net_exit sctp_defaults_exit(struct net *net)
 	net->sctp.proc_net_sctp = NULL;
 #endif
 	cleanup_sctp_mibs(net);
-	sctp_sysctl_net_unregister(net);
 }
 
 static struct pernet_operations sctp_defaults_ops = {
@@ -1451,14 +1444,24 @@ static int __net_init sctp_ctrlsock_init(struct net *net)
 	status = sctp_ctl_sock_init(net);
 	if (status)
 		pr_err("Failed to initialize the SCTP control sock\n");
+	else
+		status = sctp_sysctl_net_register(net);
+
+	if (status && net->sctp.ctl_sock) {
+		inet_ctl_sock_destroy(net->sctp.ctl_sock);
+		net->sctp.ctl_sock = NULL;
+	}
 
 	return status;
 }
 
 static void __net_exit sctp_ctrlsock_exit(struct net *net)
 {
+	sctp_sysctl_net_unregister(net);
+
 	/* Free the control endpoint.  */
 	inet_ctl_sock_destroy(net->sctp.ctl_sock);
+	net->sctp.ctl_sock = NULL;
 }
 
 static struct pernet_operations sctp_ctrlsock_ops = {
diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 15e7db9a3ab2..fca840484ebf 100644
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -615,11 +615,16 @@ int sctp_sysctl_net_register(struct net *net)
 
 void sctp_sysctl_net_unregister(struct net *net)
 {
+	struct ctl_table_header *header = net->sctp.sysctl_header;
 	const struct ctl_table *table;
 
-	table = net->sctp.sysctl_header->ctl_table_arg;
-	unregister_net_sysctl_table(net->sctp.sysctl_header);
+	if (!header)
+		return;
+
+	table = header->ctl_table_arg;
+	unregister_net_sysctl_table(header);
 	kfree(table);
+	net->sctp.sysctl_header = NULL;
 }
 
 static struct ctl_table_header *sctp_sysctl_header;
-- 
2.43.0

[PATCH net v2 2/2] sctp: close UDP tunnel sockets during netns teardown

[Ren Wei]

From: Zhiling Zou <roxy520tt@gmail.com>

proc_sctp_do_udp_port() starts per-net SCTP UDP tunneling sockets when
net.sctp.udp_port is set, and stops/restarts them when the sysctl value
changes. The netns exit path does not stop these sockets, so a namespace
can be torn down while its SCTP UDP tunnel sockets are still installed.

Close the UDP tunnel sockets from sctp_ctrlsock_exit() after unregistering
the per-net sysctl table. This prevents new sysctl writes from racing in
while the sockets are being released, and closes the sockets before the
control socket is destroyed.

Fixes: 046c052b475e ("sctp: enable udp tunneling socks")
Cc: stable@vger.kernel.org
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/b9f1f02b0780ad6a719e2413f5f0bb8eb7702d94.1782585631.git.roxy520tt%40gmail.com
Signed-off-by: Zhiling Zou <roxy520tt@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
---
 net/sctp/protocol.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index f5fe6ddf0d7d..5dbc7e9e8f06 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1458,6 +1458,7 @@ static int __net_init sctp_ctrlsock_init(struct net *net)
 static void __net_exit sctp_ctrlsock_exit(struct net *net)
 {
 	sctp_sysctl_net_unregister(net);
+	sctp_udp_sock_stop(net);
 
 	/* Free the control endpoint.  */
 	inet_ctl_sock_destroy(net->sctp.ctl_sock);
-- 
2.43.0