[PATCH net v3 1/2] sctp: avoid auth_enable sysctl UAF during netns teardown
From: Ren Wei <hidden>
Date: 2026-07-15 01:50:57
Also in:
linux-sctp
Subsystem:
networking [general], sctp protocol, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Marcelo Ricardo Leitner, Xin Long, Linus Torvalds
From: Zhiling Zou <redacted>
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 <redacted>
Reported-by: Yifan Wu <redacted>
Reported-by: Juefei Pu <redacted>
Reported-by: Xin Liu <redacted>
Co-developed-by: Qi Tang <redacted>
Signed-off-by: Qi Tang <redacted>
Signed-off-by: Zhiling Zou <redacted>
Signed-off-by: Ren Wei <redacted>
---
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(-)
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index cf335494bffe..49d9740b1e0f 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c@@ -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 = {
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