RE: [PATCH 5.10.y-cip] can: rcar_canfd: rcar_canfd_channel_probe(): make sure we free CAN network device

From: Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>
To: Pavel Machek <pavel@denx.de>
Cc: "cip-dev@lists.cip-project.org" <cip-dev@lists.cip-project.org>,
	Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>,
	Biju Das <biju.das.jz@bp.renesas.com>
Subject: RE: [PATCH 5.10.y-cip] can: rcar_canfd: rcar_canfd_channel_probe(): make sure we free CAN network device
Date: Wed, 26 Jan 2022 22:34:13 +0000	[thread overview]
Message-ID: <OSZPR01MB7019A1C696667D60C8F1EBF2AA209@OSZPR01MB7019.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <20220126221249.GB26019@duo.ucw.cz>

Hi Pavel,

Thank you for the review.

> -----Original Message-----
> From: Pavel Machek <pavel@denx.de>
> Sent: 26 January 2022 22:13
> To: Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>
> Cc: cip-dev@lists.cip-project.org; Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>; Pavel Machek
> <pavel@denx.de>; Biju Das <biju.das.jz@bp.renesas.com>
> Subject: Re: [PATCH 5.10.y-cip] can: rcar_canfd: rcar_canfd_channel_probe(): make sure we free CAN
> network device
> 
> Hi!
> 
> > commit 72b1e360572f9fa7d08ee554f1da29abce23f288 upstream.
> >
> > Make sure we free CAN network device in the error path. There are
> > several jumps to fail label after allocating the CAN network device
> > successfully. This patch places the free_candev() under fail label so
> > that in failure path a jump to fail label frees the CAN network
> > device.
> 
> Are they? I see fail label being unused in our 5.10 tree (but mainline uses it and I don't think we
> need it removed).
> 
It is being used [0].

> But more importantly... staring at the code some more:
> 
> 	err = register_candev(ndev);
> 	if (err) {
>                 dev_err(&pdev->dev,
> 	                "register_candev() failed, error %d\n", err);
> 	        goto fail_candev;
>         }
> 	spin_lock_init(&priv->tx_lock);
>         devm_can_led_init(ndev);
> 	gpriv->ch[priv->channel] = priv;
>         dev_info(&pdev->dev, "device registered (channel %u)\n", priv->channel)\ ;
> 	return 0;
> 
> Device is registered before being fully ready, and I don't see anything preventing the device from
> being used. Should register_candev be done last?
> 
Good catch, do agree register_candev() has to be done last.

> (And sorry for not noticing that earlier).
> 
No worries.

[0] https://git.kernel.org/pub/scm/linux/kernel/git/cip/linux-cip.git/tree/drivers/net/can/rcar/rcar_canfd.c?h=linux-5.10.y-cip#n1664

Cheers,
Prabhakar

> Best regards,
> 								Pavel
> --
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
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