From c1f3f9797c1f44a762e6f5f72520b2e520537b52 Mon Sep 17 00:00:00 2001 From: Marc Kleine-Budde Date: Tue, 15 Jul 2025 22:35:46 +0200 Subject: can: netlink: can_changelink(): fix NULL pointer deref of struct can_priv::do_set_mode 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 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 --- drivers/net/can/dev/netlink.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'drivers/net/can/dev/netlink.c') 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; -- cgit v1.2.3