linux-kernel - Re: [patch v2] mfd: vexpress: fix error handling vexpress_syscfg_regmap

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Date:	Fri, 13 Jun 2014 16:02:46 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Pawel Moll <pawel.moll@....com>
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	Olof Johansson <olof@...om.net>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	Lee Jones <lee.jones@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: Re: [patch v2] mfd: vexpress: fix error handling vexpress_syscfg_regmap_init()

On Wednesday 11 June 2014, Pawel Moll wrote:
> On Wed, 2014-06-11 at 11:17 +0100, Dan Carpenter wrote:
> > This function should be returning an ERR_PTR() on failure instead of
> > NULL.  Also there is a use after free bug if regmap_init() fails because
> > we free "func" and then dereference doing the return.
> > 
> > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> > 
> > diff --git a/drivers/misc/vexpress-syscfg.c b/drivers/misc/vexpress-syscfg.c
> > index 73068e5..3250fc1 100644
> > --- a/drivers/misc/vexpress-syscfg.c
> > +++ b/drivers/misc/vexpress-syscfg.c
> > @@ -199,7 +199,7 @@ static struct regmap *vexpress_syscfg_regmap_init(struct device *dev,
> >       func = kzalloc(sizeof(*func) + sizeof(*func->template) * num,
> >                       GFP_KERNEL);
> >       if (!func)
> > -             return NULL;
> > +             return ERR_PTR(-ENOMEM);
> >  
> >       func->syscfg = syscfg;
> >       func->num_templates = num;
> > @@ -231,10 +231,14 @@ static struct regmap *vexpress_syscfg_regmap_init(struct device *dev,
> >       func->regmap = regmap_init(dev, NULL, func,
> >                       &vexpress_syscfg_regmap_config);
> >  
> > -     if (IS_ERR(func->regmap))
> > +     if (IS_ERR(func->regmap)) {
> > +             void *err = func->regmap;
> > +
> >               kfree(func);
> > -     else
> > -             list_add(&func->list, &syscfg->funcs);
> > +             return err;
> > +     }
> > +
> > +     list_add(&func->list, &syscfg->funcs);
> >  
> >       return func->regmap;
> >  }
> 
> Uh, right. Dereferencing a freed structure. My bad. Thanks for spotting
> this!
> 
> Acked-by: Pawel Moll <pawel.moll@....com>
> 
> (nit: the subject should be "misc: vexpress:" rather then "mfd:")
> 
> Arnd, Olof, can you pick this one as an early fix or do you want me to
> queue it for rc1-based fixes branch?

I've applied it to the fixes branch now. Thanks!

	Arnd
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