can: fix handling of unmodifiable configuration options

As described in 'can: m_can: tag current CAN FD controllers as non-ISO'
(60e922cb9b7) it is possible to define fixed configuration options by
setting the according bit in 'ctrlmode' and clear it in 'ctrlmode_supported'.
This leads to the incovenience that the fixed configuration bits can not be
passed by netlink even when they have the correct values (e.g. non-ISO, FD).

This patch fixes that issue and not only allows fixed set bit values to be set
again but now requires(!) to provide these fixed values at configuration time.
A valid CAN FD configuration consists of a nominal/arbitration bittiming, a
data bittiming and a control mode with CAN_CTRLMODE_FD set - which is now
enforced by a new can_validate() function. This fix additionally removed the
inconsistency that was prohibiting the support of 'CANFD-only' controller
drivers, like the RCar CAN FD.

For this reason a new helper can_set_static_ctrlmode() has been introduced to
provide a proper interface to handle static enabled CAN controller options.

Reported-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Reviewed-by: Ramesh Shanmugasundaram  <ramesh.shanmugasundaram@bp.renesas.com>
Cc: <stable@vger.kernel.org> # >= 3.18
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 141c2a42d7edad6f9e833d7ab56068d7e2dd71bb..910c12e2638e3615084ca9f6a148030c8f2358e1 100644 (file)
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -696,11 +696,17 @@ int can_change_mtu(struct net_device *dev, int new_mtu)
        /* allow change of MTU according to the CANFD ability of the device */
        switch (new_mtu) {
        case CAN_MTU:
+               /* 'CANFD-only' controllers can not switch to CAN_MTU */
+               if (priv->ctrlmode_static & CAN_CTRLMODE_FD)
+                       return -EINVAL;
+
                priv->ctrlmode &= ~CAN_CTRLMODE_FD;
                break;
 
        case CANFD_MTU:
-               if (!(priv->ctrlmode_supported & CAN_CTRLMODE_FD))
+               /* check for potential CANFD ability */
+               if (!(priv->ctrlmode_supported & CAN_CTRLMODE_FD) &&
+                   !(priv->ctrlmode_static & CAN_CTRLMODE_FD))
                        return -EINVAL;
 
                priv->ctrlmode |= CAN_CTRLMODE_FD;
@@ -782,6 +788,35 @@ static const struct nla_policy can_policy[IFLA_CAN_MAX + 1] = {
                                = { .len = sizeof(struct can_bittiming_const) },
 };
 
+static int can_validate(struct nlattr *tb[], struct nlattr *data[])
+{
+       bool is_can_fd = false;
+
+       /* Make sure that valid CAN FD configurations always consist of
+        * - nominal/arbitration bittiming
+        * - data bittiming
+        * - control mode with CAN_CTRLMODE_FD set
+        */
+
+       if (data[IFLA_CAN_CTRLMODE]) {
+               struct can_ctrlmode *cm = nla_data(data[IFLA_CAN_CTRLMODE]);
+
+               is_can_fd = cm->flags & cm->mask & CAN_CTRLMODE_FD;
+       }
+
+       if (is_can_fd) {
+               if (!data[IFLA_CAN_BITTIMING] || !data[IFLA_CAN_DATA_BITTIMING])
+                       return -EOPNOTSUPP;
+       }
+
+       if (data[IFLA_CAN_DATA_BITTIMING]) {
+               if (!is_can_fd || !data[IFLA_CAN_BITTIMING])
+                       return -EOPNOTSUPP;
+       }
+
+       return 0;
+}
+
 static int can_changelink(struct net_device *dev,
                          struct nlattr *tb[], struct nlattr *data[])
 {
@@ -813,19 +848,31 @@ static int can_changelink(struct net_device *dev,
 
        if (data[IFLA_CAN_CTRLMODE]) {
                struct can_ctrlmode *cm;
+               u32 ctrlstatic;
+               u32 maskedflags;
 
                /* Do not allow changing controller mode while running */
                if (dev->flags & IFF_UP)
                        return -EBUSY;
                cm = nla_data(data[IFLA_CAN_CTRLMODE]);
+               ctrlstatic = priv->ctrlmode_static;
+               maskedflags = cm->flags & cm->mask;
+
+               /* check whether provided bits are allowed to be passed */
+               if (cm->mask & ~(priv->ctrlmode_supported | ctrlstatic))
+                       return -EOPNOTSUPP;
+
+               /* do not check for static fd-non-iso if 'fd' is disabled */
+               if (!(maskedflags & CAN_CTRLMODE_FD))
+                       ctrlstatic &= ~CAN_CTRLMODE_FD_NON_ISO;
 
-               /* check whether changed bits are allowed to be modified */
-               if (cm->mask & ~priv->ctrlmode_supported)
+               /* make sure static options are provided by configuration */
+               if ((maskedflags & ctrlstatic) != ctrlstatic)
                        return -EOPNOTSUPP;
 
                /* clear bits to be modified and copy the flag values */
                priv->ctrlmode &= ~cm->mask;
-               priv->ctrlmode |= (cm->flags & cm->mask);
+               priv->ctrlmode |= maskedflags;
 
                /* CAN_CTRLMODE_FD can only be set when driver supports FD */
                if (priv->ctrlmode & CAN_CTRLMODE_FD)
@@ -966,6 +1013,7 @@ static struct rtnl_link_ops can_link_ops __read_mostly = {
        .maxtype        = IFLA_CAN_MAX,
        .policy         = can_policy,
        .setup          = can_setup,
+       .validate       = can_validate,
        .newlink        = can_newlink,
        .changelink     = can_changelink,
        .get_size       = can_get_size,

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 39cf911f7a1e3c364d7818bdc6bcd162a6490951..195f15edb32e3cf03b552d7cdb9a98d76f565591 100644 (file)
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -955,7 +955,7 @@ static struct net_device *alloc_m_can_dev(void)
        priv->can.do_get_berr_counter = m_can_get_berr_counter;
 
        /* CAN_CTRLMODE_FD_NON_ISO is fixed with M_CAN IP v3.0.1 */
-       priv->can.ctrlmode = CAN_CTRLMODE_FD_NON_ISO;
+       can_set_static_ctrlmode(dev, CAN_CTRLMODE_FD_NON_ISO);
 
        /* CAN_CTRLMODE_FD_NON_ISO can not be changed with M_CAN IP v3.0.1 */
        priv->can.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK |

diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 735f9f8c4e43e5350f36bc4b39e9f8634778fd40..5261751f6bd4dec116516691cbc40a6763a6d12b 100644 (file)
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -40,8 +40,11 @@ struct can_priv {
        struct can_clock clock;
 
        enum can_state state;
-       u32 ctrlmode;
-       u32 ctrlmode_supported;
+
+       /* CAN controller features - see include/uapi/linux/can/netlink.h */
+       u32 ctrlmode;           /* current options setting */
+       u32 ctrlmode_supported; /* options that can be modified by netlink */
+       u32 ctrlmode_static;    /* static enabled options for driver/hardware */
 
        int restart_ms;
        struct timer_list restart_timer;
@@ -108,6 +111,21 @@ static inline bool can_is_canfd_skb(const struct sk_buff *skb)
        return skb->len == CANFD_MTU;
 }
 
+/* helper to define static CAN controller features at device creation time */
+static inline void can_set_static_ctrlmode(struct net_device *dev,
+                                          u32 static_mode)
+{
+       struct can_priv *priv = netdev_priv(dev);
+
+       /* alloc_candev() succeeded => netdev_priv() is valid at this point */
+       priv->ctrlmode = static_mode;
+       priv->ctrlmode_static = static_mode;
+
+       /* override MTU which was set by default in can_setup()? */
+       if (static_mode & CAN_CTRLMODE_FD)
+               dev->mtu = CANFD_MTU;
+}
+
 /* get data length from can_dlc with sanitized can_dlc */
 u8 can_dlc2len(u8 can_dlc);