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Date:   Tue, 4 Aug 2020 13:56:49 +0300
From:   Sakari Ailus <sakari.ailus@linux.intel.com>
To:     Bingbu Cao <bingbu.cao@linux.intel.com>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Bingbu Cao <bingbu.cao@intel.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] nvmem: core: add sanity check in nvmem_device_read()
Message-ID: <20200804105649.GG13316@paasikivi.fi.intel.com>
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On Tue, Aug 04, 2020 at 06:44:27PM +0800, Bingbu Cao wrote:
> 
> On 8/4/20 6:03 PM, Srinivas Kandagatla wrote:
> > 
> > 
> > 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@intel.com>
> >>> ---
> >>> ? 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 and Sakari, thanks for your review.
> 
> Is it OK just return INVAL with simple check like below?
> 
> if (bytes + offset > nvmem->size ||
>     bytes != round_down(bytes, nvmem->word_size))
>         return -EINVAL;

This changes what is currently supported so I'd say no.

-- 
Sakari Ailus