* [PATCH net] can: netlink: can_changelink(): fix NULL pointer deref of struct can_priv::do_set_mode
2025-07-22 10:58 [PATCH net 0/1] pull-request: can 2025-07-22 Marc Kleine-Budde
@ 2025-07-22 10:58 ` Marc Kleine-Budde
2025-07-23 1:50 ` patchwork-bot+netdevbpf
0 siblings, 1 reply; 3+ messages in thread
From: Marc Kleine-Budde @ 2025-07-22 10:58 UTC (permalink / raw)
To: netdev; +Cc: davem, kuba, linux-can, kernel, Marc Kleine-Budde, Andrei Lalaev
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: 39549eef3587 ("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>
---
drivers/net/can/dev/dev.c | 12 +++++++++---
drivers/net/can/dev/netlink.c | 12 ++++++++++++
2 files changed, 21 insertions(+), 3 deletions(-)
diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c
index ea8c807af4d8..3913971125de 100644
--- a/drivers/net/can/dev/dev.c
+++ b/drivers/net/can/dev/dev.c
@@ -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
diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c
index a36842ace084..f0e3f0d538fb 100644
--- a/drivers/net/can/dev/netlink.c
+++ b/drivers/net/can/dev/netlink.c
@@ -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;
base-commit: b03f15c0192b184078206760c839054ae6eb4eaa
--
2.47.2
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