[RFC PATCH v2 1/8] landlock: Fix non-TCP sockets restriction

[Mikhail Ivanov]

Do not check TCP access right if socket protocol is not IPPROTO_TCP.
LANDLOCK_ACCESS_NET_BIND_TCP and LANDLOCK_ACCESS_NET_CONNECT_TCP
should not restrict bind(2) and connect(2) for non-TCP protocols
(SCTP, MPTCP, SMC).

sk_is_tcp() is used for this to check address family of the socket
before doing INET-specific address length validation. This is required
for error consistency.

Closes: https://github.com/landlock-lsm/linux/issues/40
Fixes: fff69fb03dde ("landlock: Support network rules with TCP bind and connect")
Signed-off-by: Mikhail Ivanov <ivanov.mikhail1 at huawei-partners.com>
---

Changes since v1:
* Validate socket family (=INET{,6}) before any other checks
  with sk_is_tcp().
---
 security/landlock/net.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/landlock/net.c b/security/landlock/net.c
index fdc1bb0a9c5d..1e80782ba239 100644
--- a/security/landlock/net.c
+++ b/security/landlock/net.c
@@ -66,8 +66,8 @@ static int current_check_access_socket(struct socket *const sock,
 	if (WARN_ON_ONCE(dom->num_layers < 1))
 		return -EACCES;
 
-	/* Checks if it's a (potential) TCP socket. */
-	if (sock->type != SOCK_STREAM)
+	/* Do not restrict non-TCP sockets. */
+	if (!sk_is_tcp(sock->sk))
 		return 0;
 
 	/* Checks for minimal header length to safely read sa_family. */
-- 
2.34.1