can: j1939: recvmsg(): allow MSG_CMSG_COMPAT flag

commit 1db080cbdbab28752bbb1c86d64daf96253a5da1 upstream.

The control message provided by J1939 support MSG_CMSG_COMPAT but
blocked recvmsg() syscalls that have set this flag, i.e. on 32bit user
space on 64 bit kernels.

Link: https://github.com/hartkopp/can-isotp/issues/59
Cc: Oleksij Rempel <o.rempel@pengutronix.de>
Suggested-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Link: https://lore.kernel.org/20230505110308.81087-3-mkl@pengutronix.de
Cc: stable@vger.kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index 7e90f9e61d9bc5bac7e903fed4c8a7eadc7a8906..1790469b25808a8357e92ee3e42ffef9c06c0422 100644 (file)
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -798,7 +798,7 @@ static int j1939_sk_recvmsg(struct socket *sock, struct msghdr *msg,
        struct j1939_sk_buff_cb *skcb;
        int ret = 0;
 
-       if (flags & ~(MSG_DONTWAIT | MSG_ERRQUEUE))
+       if (flags & ~(MSG_DONTWAIT | MSG_ERRQUEUE | MSG_CMSG_COMPAT))
                return -EINVAL;
 
        if (flags & MSG_ERRQUEUE)