From:   Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
To:     davem@davemloft.net
Cc:     linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
Subject: [PATCH net-next] scm: fix MSG_CTRUNC setting condition for SO_PASSSEC
Date:   Sun, 26 Feb 2023 21:17:30 +0100
Message-Id: <20230226201730.515449-1-aleksandr.mikhalitsyn@canonical.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Currently, we set MSG_CTRUNC flag is we have no
msg_control buffer provided and SO_PASSCRED is set
or if we have pending SCM_RIGHTS.

For some reason we have no corresponding check for
SO_PASSSEC.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
---
 include/net/scm.h | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/net/scm.h b/include/net/scm.h
index 1ce365f4c256..585adc1346bd 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -105,16 +105,27 @@ static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct sc
 		}
 	}
 }
+
+static inline bool scm_has_secdata(struct socket *sock)
+{
+	return test_bit(SOCK_PASSSEC, &sock->flags);
+}
 #else
 static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
 { }
+
+static inline bool scm_has_secdata(struct socket *sock)
+{
+	return false;
+}
 #endif /* CONFIG_SECURITY_NETWORK */
 
 static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg,
 				struct scm_cookie *scm, int flags)
 {
 	if (!msg->msg_control) {
-		if (test_bit(SOCK_PASSCRED, &sock->flags) || scm->fp)
+		if (test_bit(SOCK_PASSCRED, &sock->flags) || scm->fp ||
+		    scm_has_secdata(sock))
 			msg->msg_flags |= MSG_CTRUNC;
 		scm_destroy(scm);
 		return;
-- 
2.34.1