linux-kernel - Re: [PATCH can] can: netlink: can_changelink(): allow disabling of automatic restart

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Message-ID: <20251020-gigantic-jovial-mastiff-cb8d0d-mkl@pengutronix.de>
Date: Mon, 20 Oct 2025 17:26:50 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Vincent Mailhol <mailhol@...nel.org>
Cc: kernel@...gutronix.de, linux-can@...r.kernel.org, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org, Andrei Lalaev <andrey.lalaev@...il.com>
Subject: Re: [PATCH can] can: netlink: can_changelink(): allow disabling of
 automatic restart

On 20.10.2025 13:34:42, Marc Kleine-Budde wrote:
> Since the commit c1f3f9797c1f ("can: netlink: can_changelink(): fix NULL
> pointer deref of struct can_priv::do_set_mode"), the automatic restart
> delay can only be set for devices that implement the restart handler struct
> can_priv::do_set_mode. As it makes no sense to configure a automatic
> restart for devices that doesn't support it.
> 
> However, since systemd commit 13ce5d4632e3 ("network/can: properly handle
> CAN.RestartSec=0") [1], systemd-networkd correctly handles a restart delay
> of "0" (i.e. the restart is disabled). Which means that a disabled restart
> is always configured in the kernel.
> 
> On systems with both changes active this causes that CAN interfaces that
> don't implement a restart handler cannot be brought up by systemd-networkd.
> 
> Solve this problem by allowing a delay of "0" to be configured, even if the
> device does not implement a restart handler.
> 
> [1] https://github.com/systemd/systemd/commit/13ce5d4632e395521e6205c954493c7fc1c4c6e0
> 
> Cc: stable@...r.kernel.org
> Cc: Andrei Lalaev <andrey.lalaev@...il.com>
> Reported-by: Marc Kleine-Budde <mkl@...gutronix.de>
> Closes: https://lore.kernel.org/all/20251020-certain-arrogant-vole-of-sunshine-141841-mkl@pengutronix.de
> Fixes: c1f3f9797c1f ("can: netlink: can_changelink(): fix NULL pointer deref of struct can_priv::do_set_mode")
> Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>

Applied to linux-can.

Marc

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