linux-kernel - Re: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS

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Date:	Mon, 24 Jan 2011 23:05:17 +0300
From:	Vasiliy Kulikov <segooon@...il.com>
To:	Julia Lawall <julia@...u.dk>
Cc:	Ryan Mallon <ryan@...ewatersys.com>,
	Russell King <linux@....linux.org.uk>,
	kernel-janitors@...r.kernel.org,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Andrew Victor <linux@...im.org.za>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test

On Mon, Jan 24, 2011 at 21:00 +0100, Julia Lawall wrote:
> On Tue, 25 Jan 2011, Ryan Mallon wrote:
> 
> > On 01/25/2011 08:55 AM, Julia Lawall wrote:
> > > @@ -224,7 +224,7 @@ void __init at91_clock_associate(const char *id, struct device *dev, const char
> > >  {
> > >  	struct clk *clk = clk_get(NULL, id);
> > >  
> > > -	if (!dev || !clk || !IS_ERR(clk_get(dev, func)))
> > > +	if (!dev || IS_ERR(clk) || !IS_ERR(clk_get(dev, func)))
> > >  		return;
> > 
> > I think we want:
> > 
> > 	if (!dev || !clk || IS_ERR(clk) || !IS_ERR(clk_get(dev, func)))
> > 		return;
> > 
> > Since it is valid to return a NULL clk, and we don't want to try and
> > dereference it if that is the case.
> 
> Looking at the given defintion of clk_get, I can't see how that could 
> happen:

clk_get() is defined per-architecture, sometimes it is NULL only.

> struct clk *clk_get(struct device *dev, const char *id)
> {
>         struct clk *clk;
> 
>         list_for_each_entry(clk, &clocks, node) {
>                 if (strcmp(id, clk->name) == 0)
>                         return clk;
>                 if (clk->function && (dev == clk->dev) && strcmp(id, clk->function) == 0)
>                         return clk;
>         }
> 
>         return ERR_PTR(-ENOENT);
> }
> 
> Both paths to the non-ERR_PTR return dereference clk.
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 
Vasiliy
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