Re: [PATCH] nvmem: core: add sanity check in nvmem_device_read()

[Srinivas Kandagatla]

On 04/08/2020 10:58, Sakari Ailus wrote:
> Hi Bingbu,
>
> Thank you for the patch.
>
> On Tue, Aug 04, 2020 at 05:13:56PM +0800, Bingbu Cao wrote:
> > nvmem_device_read() could be called directly once nvmem device
> > registered, the sanity check should be done before call
> > nvmem_reg_read() as cell and sysfs read did now.
> >
> > Signed-off-by: Bingbu Cao <bingbu.cao@xxxxxxxxx>
> > ---
> >   drivers/nvmem/core.c | 7 +++++++
> >   1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> > index 927eb5f6003f..c9a77993f008 100644
> > --- a/drivers/nvmem/core.c
> > +++ b/drivers/nvmem/core.c
> > @@ -1491,6 +1491,13 @@ int nvmem_device_read(struct nvmem_device *nvmem,
> >   	if (!nvmem)
> >   		return -EINVAL;
> >   
> > +	if (offset >= nvmem->size || bytes < nvmem->word_size)
> > +		return 0;
> > +
> > +	if (bytes + offset > nvmem->size)
> > +		bytes = nvmem->size - offset;
>
> The check is relevant for nvmem_device_write(), too.
>
> There are also other ways to access nvmem devices such as nvmem_cell_read
> and others alike. Should they be considered as well?

We should probably move these sanity checks to a common place like 
nvmem_reg_read() and nvmem_reg_write(), so the callers need not 
duplicate the same!

--srini

> > +
> > +	bytes = round_down(bytes, nvmem->word_size);
> >   	rc = nvmem_reg_read(nvmem, offset, buf, bytes);
> >   
> >   	if (rc)