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can: netlink: can_changelink(): fix NULL pointer deref of struct can_priv::do_set_mode

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Andrei Lalaev reported a NULL pointer deref when a CAN device is
restarted from Bus Off and the driver does not implement the struct
can_priv::do_set_mode callback.

There are 2 code path that call struct can_priv::do_set_mode:
- directly by a manual restart from the user space, via
  can_changelink()
- delayed automatic restart after bus off (deactivated by default)

To prevent the NULL pointer deference, refuse a manual restart or
configure the automatic restart delay in can_changelink() and report
the error via extack to user space.

As an additional safety measure let can_restart() return an error if
can_priv::do_set_mode is not set instead of dereferencing it
unchecked.

Reported-by: Andrei Lalaev <andrey.lalaev@gmail.com>
Closes: https://lore.kernel.org/all/20250714175520.307467-1-andrey.lalaev@gmail.com
Fixes: 39549eef35 ("can: CAN Network device driver and Netlink interface")
Link: https://patch.msgid.link/20250718-fix-nullptr-deref-do_set_mode-v1-1-0b520097bb96@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Marc Kleine-Budde 2025-07-15 22:35:46 +02:00
parent b03f15c019
commit c1f3f9797c
2 changed files with 21 additions and 3 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

12
drivers/net/can/dev/dev.c
View file

@ -145,13 +145,16 @@ void can_change_state(struct net_device *dev, struct can_frame *cf,
EXPORT_SYMBOL_GPL(can_change_state);
/* CAN device restart for bus-off recovery */
static void can_restart(struct net_device *dev)
static int can_restart(struct net_device *dev)
{
struct can_priv *priv = netdev_priv(dev);
struct sk_buff *skb;
struct can_frame *cf;
int err;
if (!priv->do_set_mode)
return -EOPNOTSUPP;
if (netif_carrier_ok(dev))
netdev_err(dev, "Attempt to restart for bus-off recovery, but carrier is OK?\n");
@ -173,10 +176,14 @@ static void can_restart(struct net_device *dev)
if (err) {
netdev_err(dev, "Restart failed, error %pe\n", ERR_PTR(err));
netif_carrier_off(dev);
return err;
} else {
netdev_dbg(dev, "Restarted\n");
priv->can_stats.restarts++;
}
return 0;
}
static void can_restart_work(struct work_struct *work)
@ -201,9 +208,8 @@ int can_restart_now(struct net_device *dev)
return -EBUSY;
cancel_delayed_work_sync(&priv->restart_work);
can_restart(dev);
return 0;
return can_restart(dev);
}
/* CAN bus-off

12
drivers/net/can/dev/netlink.c
View file

@ -285,6 +285,12 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
}
if (data[IFLA_CAN_RESTART_MS]) {
if (!priv->do_set_mode) {
NL_SET_ERR_MSG(extack,
"Device doesn't support restart from Bus Off");
return -EOPNOTSUPP;
}
/* Do not allow changing restart delay while running */
if (dev->flags & IFF_UP)
return -EBUSY;
@ -292,6 +298,12 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
}
if (data[IFLA_CAN_RESTART]) {
if (!priv->do_set_mode) {
NL_SET_ERR_MSG(extack,
"Device doesn't support restart from Bus Off");
return -EOPNOTSUPP;
}
/* Do not allow a restart while not running */
if (!(dev->flags & IFF_UP))
return -EINVAL;