sctp: avoid auth_enable sysctl UAF during netns teardown
Subsystems (3)
A message that is not in the archive (sent off-list or not yet received): [email protected]
PATCH v3 1/2 sctp: avoid auth_enable sysctl UAF during netns teardown
From: Zhiling Zou <[email protected]>
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.
---
Changes in v3:
- Follow Xin Long's suggestion and return immediately when sctp_ctl_sock_init() fails.
- Keep per-net SCTP sysctl registration in a separate success path after the control socket has been created.
net/sctp/protocol.c | 20 ++++++++++++-------- net/sctp/sysctl.c | 9 +++++++-- 2 files changed, 19 insertions(+), 10 deletions(-)
net/sctp/protocol.c +12 -8
@@ -1383,10 +1383,6 @@ 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)
@@ -1420,8 +1416,6 @@ 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; }
@@ -1436,7 +1430,6 @@ 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 = {
@@ -1450,16 +1443,27 @@ static int __net_init sctp_ctrlsock_init(struct net *net)/* Initialize the control inode/socket for handling OOTB packets. */ status =sctp_ctl_sock_init (net); -if (status) +if (status) {pr_err ("Failed to initialize the SCTP control sock\n" ); +return status; + } + + status =sctp_sysctl_net_register (net); +if (status) { +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 = {
net/sctp/sysctl.c +7 -2
@@ -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;
Signature · 1 line
2.43.0
Quoted 25 lines · Ren Wei
From: Zhiling Zou <[email protected]>
proc_sctp_do_auth()updates the SCTP control socket after changing net.sctp.auth_enable. The handler gets the per-net SCTP state fromctl->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 fromsctp_ctrlsock_init(). This exposed a window during initialization whereauth_enablewas writable beforenet->sctp.ctl_sockexisted, and a teardown window whereauth_enablestayed writable afterinet_ctl_sock_destroy()had released the control socket.Move the per-net SCTP sysctl registration into
sctp_ctrlsock_init()aftersctp_ctl_sock_init()succeeds, and unregister the sysctl table before destroying the control socket insctp_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.
Quoted 10 lines
Fixes 15649fd5415e ("sctp: sysctl: auth_enable: avoid using current->nsproxy")Reported-by Yuan Tan <[email protected]>Reported-by Yifan Wu <[email protected]>Reported-by Juefei Pu <[email protected]>Reported-by Xin Liu <[email protected]>Co-developed-by Qi Tang <[email protected]>Signed-off-by Qi Tang <[email protected]>Signed-off-by Zhiling Zou <[email protected]>Signed-off-by Ren Wei <[email protected]>
This series was applied to netdev/net.git (main) by Jakub Kicinski <[email protected]>:
Hello:
This series was applied to netdev/net.git (main)
by Jakub Kicinski <[email protected]>:
Quoted 8 lines · On Wed, 15 Jul 2026 09:50:10 +0800 you wrote:
From: Zhiling Zou <[email protected]>
proc_sctp_do_auth()updates the SCTP control socket after changing net.sctp.auth_enable. The handler gets the per-net SCTP state fromctl->data, so an already opened sysctl file can still target a network namespace while that namespace is being torn down.[...]
Here is the summary with links:
- [net,v3,1/2] sctp: avoid auth_enable sysctl UAF during netns teardown
https://git.kernel.org/netdev/net/c/f8d5e7846025 - [net,v3,2/2] sctp: close UDP tunnel sockets during netns teardown https://git.kernel.org/netdev/net/c/ffb2bd7ade36
You are awesome, thank you!
Signature · 2 lines
Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
PATCH v3 2/2 sctp: close UDP tunnel sockets during netns teardown
In reply to a message not in the archiveFrom: Zhiling Zou <[email protected]>
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.
---
Changes in v3:
- No code changes.
net/sctp/protocol.c | 1 + 1 file changed, 1 insertion(+)
net/sctp/protocol.c +1 -0
@@ -1460,6 +1460,7 @@ 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);
Signature · 1 line
2.43.0
Re: [PATCH net v3 2/2] sctp: close UDP tunnel sockets during netns teardown
Quoted 39 lines · Ren Wei
From: Zhiling Zou <[email protected]>
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")Reported-by Sashiko <[email protected]>Signed-off-by Zhiling Zou <[email protected]>Signed-off-by Ren Wei <[email protected]>---
Changes in v3:
- No code changes.net/sctp/protocol.c | 1 + 1 file changed, 1 insertion(+)net/sctp/protocol.c +1
-1@@ -1460,6 +1460,7 @@ 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); --
Quoted 2 lines
2.43.0