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[87.106.108.193]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48323c0296dsm200490325e9.1.2026.02.08.15.11.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Feb 2026 15:11:19 -0800 (PST) From: =?UTF-8?q?G=C3=BCnther=20Noack?= To: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , "John Johansen" , "Paul Moore" , James Morris , "Serge E . Hallyn" Cc: =?UTF-8?q?G=C3=BCnther=20Noack?= , Tingmao Wang , Justin Suess , linux-security-module@vger.kernel.org, "Samasth Norway Ananda" , "Matthieu Buffet" , "Mikhail Ivanov" , konstantin.meskhidze@huawei.com, "Demi Marie Obenour" , "Alyssa Ross" , "Jann Horn" , "Tahera Fahimi" , Simon Horman , netdev@vger.kernel.org, Alexander Viro , Christian Brauner Subject: [PATCH v4 1/6] lsm: Add LSM hook security_unix_find Date: Mon, 9 Feb 2026 00:10:11 +0100 Message-ID: <20260208231017.114343-2-gnoack3000@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260208231017.114343-1-gnoack3000@gmail.com> References: <20260208231017.114343-1-gnoack3000@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Justin Suess Add a 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. Cc: Günther Noack Cc: Tingmao Wang Signed-off-by: Justin Suess --- include/linux/lsm_hook_defs.h | 5 +++++ include/linux/security.h | 11 +++++++++++ net/unix/af_unix.c | 9 +++++++++ security/security.c | 20 ++++++++++++++++++++ 4 files changed, 45 insertions(+) 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 83a646d72f6f..99a33d8eb28d 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -1931,6 +1931,17 @@ 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); diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index d0511225799b..db9d279b3883 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1226,10 +1226,19 @@ static struct sock *unix_find_bsd(struct sockaddr_un *sunaddr, int addr_len, if (!S_ISSOCK(inode->i_mode)) goto path_put; + err = -ECONNREFUSED; sk = unix_find_socket_byinode(inode); if (!sk) goto path_put; + /* + * We call the hook because we know that the inode is a socket + * and we hold a valid reference to it via the path. + */ + err = security_unix_find(&path, sk, flags); + if (err) + goto sock_put; + err = -EPROTOTYPE; if (sk->sk_type == type) touch_atime(&path); diff --git a/security/security.c b/security/security.c index 31a688650601..9e9515955098 100644 --- a/security/security.c +++ b/security/security.c @@ -4731,6 +4731,26 @@ int security_mptcp_add_subflow(struct sock *sk, struct sock *ssk) #endif /* CONFIG_SECURITY_NETWORK */ +#if defined(CONFIG_SECURITY_NETWORK) && defined(CONFIG_SECURITY_PATH) +/* + * security_unix_find() - Check if a named AF_UNIX socket can connect + * @path: path of the socket being connected to + * @other: peer sock + * @flags: flags associated with the socket + * + * This hook is called to check permissions before connecting to a named + * AF_UNIX socket. + * + * Return: Returns 0 if permission is granted. + */ +int security_unix_find(const struct path *path, struct sock *other, int flags) +{ + return call_int_hook(unix_find, path, other, flags); +} +EXPORT_SYMBOL(security_unix_find); + +#endif /* CONFIG_SECURITY_NETWORK && CONFIG_SECURITY_PATH */ + #ifdef CONFIG_SECURITY_INFINIBAND /** * security_ib_pkey_access() - Check if access to an IB pkey is allowed -- 2.52.0