CVE-2026-68162sctp: avoid auth_enable sysctl UAF during netns teardown

Official description

In the Linux kernel, the following vulnerability has been resolved: sctp: avoid auth_enable sysctl UAF during netns teardown 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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/19573dcddb8819fd68d6cd1f916c1c99c3fa4ff4
• https://git.kernel.org/stable/c/ceb7190b5c873d4a1267a1600c5aa52c600e929f
• https://git.kernel.org/stable/c/fd66854a22661929245f3d2b244c432bc8b1a150
• https://git.kernel.org/stable/c/158f3cc332dc53f43ec20060233d7c3cecd6d912
• https://git.kernel.org/stable/c/66700c0719675e0e118ae83b2d7168dacd69dd3d
• https://git.kernel.org/stable/c/626bda8cfe43dff19a9833ff6ba055a817b5455c
• https://git.kernel.org/stable/c/be6aae9d1b91c603adb35872d37d40e83daf8758
• https://git.kernel.org/stable/c/a50e73488e0bbdd262b3be3c9a1d8dd078382381
• https://git.kernel.org/stable/c/f8d5e7846025f4ab15a461235f8ebae9094a361a