Re: [patch v2] mfd: vexpress: fix error handling vexpress_syscfg_regmap_init()

[Greg Kroah-Hartman]

On Wed, Jun 11, 2014 at 11:33:20AM +0100, 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@xxxxxxxxxx>
> > 
> > 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@xxxxxxx>
> 
> (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 can queue it up.

thanks,

greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/