linux-kernel - Re: [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the NVMEM framework

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Date:	Wed, 2 Mar 2016 23:26:39 +0100
From:	Andrew Lunn <andrew@...n.ch>
To:	Vladimir Zapolskiy <vz@...ia.com>
Cc:	GregKH <greg@...ah.com>, srinivas.kandagatla@...aro.org,
	maxime.ripard@...e-electrons.com, wsa@...-dreams.de,
	broonie@...nel.org, linux-kernel@...r.kernel.org,
	pantelis.antoniou@...sulko.com, bgolaszewski@...libre.com
Subject: Re: [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the
 NVMEM framework

> >  static ssize_t
> > -eeprom_93xx46_bin_read(struct file *filp, struct kobject *kobj,
> > -		       struct bin_attribute *bin_attr,
> > -		       char *buf, loff_t off, size_t count)
> > +eeprom_93xx46_read(struct eeprom_93xx46_dev *edev, char *buf,
> > +		   unsigned off, size_t count)
> >  {
> > -	struct eeprom_93xx46_dev *edev;
> > -	struct device *dev;
> >  	ssize_t ret = 0;
> >  
> > -	dev = kobj_to_dev(kobj);
> > -	edev = dev_get_drvdata(dev);
> > +	if (unlikely(off >= edev->size))
> > +		return 0;
> > +	if ((off + count) > edev->size)
> > +		count = edev->size - off;
> > +	if (unlikely(!count))
> > +		return count;
> >  
> 
> I'm scratching my head, do you want to kind of revert
> the change https://lkml.org/lkml/2015/7/26/89 ? Why?

Hi Vladimir

I had not noticed you had removed this.
 
> If you know regmap_config.max_register, then all necessary
> boundary checks can be done inside NVMEM core.

You don't have to use NVMEM, you could use the regmap directly. It is
a public API. Also, during implementation, i did manage to get out of
bounds read passed into the drivers and they caused a crash. That
might of been AT24, i don't remember, but verifying is better than
possible crashing.

> > +/*
> > + * Provide a regmap interface, which is registered with the NVMEM
> > + * framework
> > +*/
> > +static int eeprom_93xx46_regmap_read(void *context, const void *reg,
> > +				     size_t reg_size, void *val,
> > +				     size_t val_size)
> > +{
> > +	struct eeprom_93xx46_dev *eeprom_93xx46 = context;
> > +	off_t offset = *(u32 *)reg;
> > +	int err;
> > +
> > +	err = eeprom_93xx46_read(eeprom_93xx46, val, offset, val_size);
> > +	if (err)
> > +		return err;
> > +	return 0;
> 
> return eeprom_93xx46_read(eeprom_93xx46, val, offset, val_size);

As i've said a few times now to a few different people reviewing these
patches, regmap wants either an error code or 0.

	 Andrew