can: raw: instantly reject disabled CAN frames

For real CAN interfaces the CAN_CTRLMODE_FD and CAN_CTRLMODE_XL control
modes indicate whether an interface can handle those CAN FD/XL frames.

In the case a CAN XL interface is configured in CANXL-only mode with
disabled error-signalling neither CAN CC nor CAN FD frames can be sent.

The checks are now performed on CAN_RAW sockets to give an instant feedback
to the user when writing unsupported CAN frames to the interface or when
the CAN interface is in read-only mode.

Fixes: 1a620a723853 ("can: raw: instantly reject unsupported CAN frames")
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20260109144135.8495-4-socketcan@hartkopp.net
[mkl: fix dev reference leak]
Link: https://lore.kernel.org/all/0636c732-2e71-4633-8005-dfa85e1da445@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/net/can/raw.c b/net/can/raw.c
index f36a83d3447cfd6d70364dbd49534507f059660e..12293363413ce6906b068e45d000d188836f6a91 100644 (file)
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -49,8 +49,8 @@
 #include <linux/if_arp.h>
 #include <linux/skbuff.h>
 #include <linux/can.h>
+#include <linux/can/can-ml.h>
 #include <linux/can/core.h>
-#include <linux/can/dev.h> /* for can_is_canxl_dev_mtu() */
 #include <linux/can/skb.h>
 #include <linux/can/raw.h>
 #include <net/sock.h>
@@ -892,20 +892,21 @@ static void raw_put_canxl_vcid(struct raw_sock *ro, struct sk_buff *skb)
        }
 }
 
-static unsigned int raw_check_txframe(struct raw_sock *ro, struct sk_buff *skb, int mtu)
+static unsigned int raw_check_txframe(struct raw_sock *ro, struct sk_buff *skb,
+                                     struct net_device *dev)
 {
-       /* Classical CAN -> no checks for flags and device capabilities */
-       if (can_is_can_skb(skb))
+       /* Classical CAN */
+       if (can_is_can_skb(skb) && can_cap_enabled(dev, CAN_CAP_CC))
                return CAN_MTU;
 
-       /* CAN FD -> needs to be enabled and a CAN FD or CAN XL device */
+       /* CAN FD */
        if (ro->fd_frames && can_is_canfd_skb(skb) &&
-           (mtu == CANFD_MTU || can_is_canxl_dev_mtu(mtu)))
+           can_cap_enabled(dev, CAN_CAP_FD))
                return CANFD_MTU;
 
-       /* CAN XL -> needs to be enabled and a CAN XL device */
+       /* CAN XL */
        if (ro->xl_frames && can_is_canxl_skb(skb) &&
-           can_is_canxl_dev_mtu(mtu))
+           can_cap_enabled(dev, CAN_CAP_XL))
                return CANXL_MTU;
 
        return 0;
@@ -944,6 +945,12 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
        if (!dev)
                return -ENXIO;
 
+       /* no sending on a CAN device in read-only mode */
+       if (can_cap_enabled(dev, CAN_CAP_RO)) {
+               err = -EACCES;
+               goto put_dev;
+       }
+
        skb = sock_alloc_send_skb(sk, size + sizeof(struct can_skb_priv),
                                  msg->msg_flags & MSG_DONTWAIT, &err);
        if (!skb)
@@ -961,7 +968,7 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
        err = -EINVAL;
 
        /* check for valid CAN (CC/FD/XL) frame content */
-       txmtu = raw_check_txframe(ro, skb, READ_ONCE(dev->mtu));
+       txmtu = raw_check_txframe(ro, skb, dev);
        if (!txmtu)
                goto free_skb;