From eb25e202b3d60cdc239f14e0e5f6f7465fcc506c Mon Sep 17 00:00:00 2001 From: Justin Suess Date: Fri, 27 Mar 2026 17:48:26 +0100 Subject: lsm: Add LSM hook security_unix_find MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add an LSM hook security_unix_find. This hook is called to check the path of a named UNIX socket before a connection is initiated. The peer socket may be inspected as well. Why existing hooks are unsuitable: Existing socket hooks, security_unix_stream_connect(), security_unix_may_send(), and security_socket_connect() don't provide TOCTOU-free / namespace independent access to the paths of sockets. (1) We cannot resolve the path from the struct sockaddr in existing hooks. This requires another path lookup. A change in the path between the two lookups will cause a TOCTOU bug. (2) We cannot use the struct path from the listening socket, because it may be bound to a path in a different namespace than the caller, resulting in a path that cannot be referenced at policy creation time. Consumers of the hook wishing to reference @other are responsible for acquiring the unix_state_lock and checking for the SOCK_DEAD flag therein, ensuring the socket hasn't died since lookup. Cc: Günther Noack Cc: Tingmao Wang Cc: Mickaël Salaün Cc: Paul Moore Signed-off-by: Justin Suess Signed-off-by: Günther Noack Reviewed-by: Georgia Garcia Acked-by: Paul Moore Link: https://lore.kernel.org/r/20260327164838.38231-2-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün --- include/linux/lsm_hook_defs.h | 5 +++++ include/linux/security.h | 11 +++++++++++ 2 files changed, 16 insertions(+) (limited to 'include/linux') diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 8c42b4bde09c..7a0fd3dbfa29 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -317,6 +317,11 @@ LSM_HOOK(int, 0, post_notification, const struct cred *w_cred, LSM_HOOK(int, 0, watch_key, struct key *key) #endif /* CONFIG_SECURITY && CONFIG_KEY_NOTIFICATIONS */ +#if defined(CONFIG_SECURITY_NETWORK) && defined(CONFIG_SECURITY_PATH) +LSM_HOOK(int, 0, unix_find, const struct path *path, struct sock *other, + int flags) +#endif /* CONFIG_SECURITY_NETWORK && CONFIG_SECURITY_PATH */ + #ifdef CONFIG_SECURITY_NETWORK LSM_HOOK(int, 0, unix_stream_connect, struct sock *sock, struct sock *other, struct sock *newsk) diff --git a/include/linux/security.h b/include/linux/security.h index ee88dd2d2d1f..c2d665cbfcfb 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -1932,6 +1932,17 @@ static inline int security_mptcp_add_subflow(struct sock *sk, struct sock *ssk) } #endif /* CONFIG_SECURITY_NETWORK */ +#if defined(CONFIG_SECURITY_NETWORK) && defined(CONFIG_SECURITY_PATH) + +int security_unix_find(const struct path *path, struct sock *other, int flags); + +#else /* CONFIG_SECURITY_NETWORK && CONFIG_SECURITY_PATH */ +static inline int security_unix_find(const struct path *path, struct sock *other, int flags) +{ + return 0; +} +#endif /* CONFIG_SECURITY_NETWORK && CONFIG_SECURITY_PATH */ + #ifdef CONFIG_SECURITY_INFINIBAND int security_ib_pkey_access(void *sec, u64 subnet_prefix, u16 pkey); int security_ib_endport_manage_subnet(void *sec, const char *name, u8 port_num); -- cgit v1.2.3