linux-kernel - RE: [PATCH V2 2/2] clocksource: imx-gpt: add necessary kfree to avoid resource leak

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Date:   Tue, 6 Nov 2018 09:12:37 +0000
From:   Anson Huang <anson.huang@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH V2 2/2] clocksource: imx-gpt: add necessary kfree to avoid
 resource leak

Hi, Daniel

Best Regards!
Anson Huang

> -----Original Message-----
> From: Daniel Lezcano [mailto:daniel.lezcano@...aro.org]
> Sent: 2018年11月6日 17:06
> To: Anson Huang <anson.huang@....com>; tglx@...utronix.de;
> linux-kernel@...r.kernel.org
> Cc: dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH V2 2/2] clocksource: imx-gpt: add necessary kfree to avoid
> resource leak
> 
> 
> Hi Anson,
> 
> On 06/11/2018 02:38, Anson Huang wrote:
> > Hi, Daniel
> >
> > Best Regards!
> > Anson Huang
> >
> >> -----Original Message-----
> >> From: Daniel Lezcano [mailto:daniel.lezcano@...aro.org]
> >> Sent: 2018年11月5日 21:35
> >> To: Anson Huang <anson.huang@....com>; tglx@...utronix.de;
> >> linux-kernel@...r.kernel.org
> >> Cc: dl-linux-imx <linux-imx@....com>
> >> Subject: Re: [PATCH V2 2/2] clocksource: imx-gpt: add necessary kfree
> >> to avoid resource leak
> >>
> >> Hi Anson,
> >>
> >> On 05/11/2018 02:10, Anson Huang wrote:
> >>> kfree should be called to free resource in error path before return.
> >>>
> >>> Signed-off-by: Anson Huang <Anson.Huang@....com>
> >>> ---
> >>>  drivers/clocksource/timer-imx-gpt.c | 8 ++++++--
> >>>  1 file changed, 6 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/clocksource/timer-imx-gpt.c
> >>> b/drivers/clocksource/timer-imx-gpt.c
> >>> index a3d6ccb..0f78b30 100644
> >>> --- a/drivers/clocksource/timer-imx-gpt.c
> >>> +++ b/drivers/clocksource/timer-imx-gpt.c
> >>> @@ -477,12 +477,16 @@ static int __init mxc_timer_init_dt(struct
> >> device_node *np,  enum imx_gpt_type t
> >>>  		return -ENOMEM;
> >>>
> >>>  	imxtm->base = of_iomap(np, 0);
> >>> -	if (!imxtm->base)
> >>> +	if (!imxtm->base) {
> >>> +		kfree(imxtm);
> >>>  		return -ENXIO;
> >>> +	}
> >>>
> >>>  	imxtm->irq = irq_of_parse_and_map(np, 0);
> >>> -	if (imxtm->irq <= 0)
> >>> +	if (imxtm->irq <= 0) {
> >>> +		kfree(imxtm);
> >>>  		return -EINVAL;
> >>> +	}
> >>>
> >>>  	imxtm->clk_ipg = of_clk_get_by_name(np, "ipg");
> >>
> >> Please convert to timer-of API.
> >
> > This patch mainly to fix the potential resource leak issue, for
> > converting to timer-of API, should I add another patch for it? Since
> > it is a different subject.
> 
> Actually I was unclear. The patch is duplicating the kfree in the error path,
> usually a rollback routine should be provided.
> 
> So instead of creating this rollback path, you can directly use the timer-of
> which contains the error check and rollback.

I understand the timer-of can save some code in timer driver, but current GPT
driver is kind of complicated in order to support so many i.MX platforms with
different GPT design, change it to timer-of will need some effort and I think we
can do it later. If the duplicating kfree in error path confuses you, I can change
it to rollback path you said. Below are 2 options in my mind:

1. add kfree to rollback path;
2. skip this patch, just apply 1/2 patch, and let me find some time to change GPT
driver using timer-of. 

Which one do you prefer? Thanks.

Anson.

> 
> 
> 
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