Re: [PATCH 2/2] regmap: Add range check in _regmap_raw_write()

[Srinivas Kandagatla]

On 19/02/15 10:31, Mark Brown wrote:
> On Thu, Feb 19, 2015 at 08:40:55AM +0000, Srinivas Kandagatla wrote:
> > regmap_bulk_write() ends up using the path that invokes _regmap_raw_write(),
> > however _regmap_raw_write() never checks if the registers that are accessed
> > are actually within the accessible range. This results in kernel crashes when
> > trying to access registers beyond max_registers.
> >
> > This patch just adds check before accessing the register range.
>
> >   	/* Check for unwritable registers before we start */
> > -	if (map->writeable_reg)
> > -		for (i = 0; i < val_len / map->format.val_bytes; i++)
> > -			if (!map->writeable_reg(map->dev,
> > -						reg + (i * map->reg_stride)))
> > -				return -EINVAL;
> > +	for (i = 0; i < count; i++)
> > +		if (!regmap_writeable(map, reg + (i * map->reg_stride)))
> > +			return -EINVAL;
>
> Your changelog doesn't correspond to what the code is actually doing
> here...  what you're actually doing here is replacing an open coding of
> regmap_writeable() with calls to the function.
>
> The same papering over the cracks concerns do apply here as well, it's
> not immediately obvious that this is a good fix for the issue you
> describe.
Only reason for me to send this patch was that fact that 
_regmap_raw_write() also suffers from same issue as _regmap_raw_read(), 
which is "access beyond max_register".

Should I drop this patch?
Or
Adding similar check of max_register before the writing makes sense?


--srini
--
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/