Re: [PATCH v5 3/5] mtd: spi-nor: otp: return -EROFS if region is read-only

[Michael Walle]

Am 2021-06-04 15:07, schrieb Tudor.Ambarus@xxxxxxxxxxxxx:
> On 6/4/21 1:02 PM, Michael Walle wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know 
> > the content is safe
> >
> > SPI NOR flashes will just ignore program commands if the OTP region is
> > locked. Thus, a user might not notice that the intended write didn't 
> > end
> > up in the flash. Return -EROFS to the user in this case. From what I 
> > can
> > tell, chips/cfi_cmdset_0001.c also return this error code.
> >
> > One could optimize spi_nor_mtd_otp_range_is_locked() to read the 
> > status
> > register only once and not for every OTP region, but for that we would
> > need some more invasive changes. Given that this is
> > one-time-programmable memory and the normal access mode is reading, we
> > just live with the small overhead.
> >
> > Fixes: 069089acf88b ("mtd: spi-nor: add OTP support")
> > Signed-off-by: Michael Walle <michael@xxxxxxxx>
> > Reviewed-by: Pratyush Yadav <p.yadav@xxxxxx>
> > ---
> >  drivers/mtd/spi-nor/otp.c | 36 ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 36 insertions(+)
> >
> > diff --git a/drivers/mtd/spi-nor/otp.c b/drivers/mtd/spi-nor/otp.c
> > index 3898ed67ba1c..063f8fb68649 100644
> > --- a/drivers/mtd/spi-nor/otp.c
> > +++ b/drivers/mtd/spi-nor/otp.c
> > @@ -249,6 +249,32 @@ static int spi_nor_mtd_otp_info(struct mtd_info 
> > *mtd, size_t len,
> >         return ret;
> >  }
> >
> > +static int spi_nor_mtd_otp_range_is_locked(struct spi_nor *nor, 
> > loff_t ofs,
> > +                                          size_t len)
> > +{
> > +       const struct spi_nor_otp_ops *ops = nor->params->otp.ops;
> > +       unsigned int region;
> > +       int locked;
> > +
> > +       if (!len)
> > +               return 0;
> > +
>
> You won't need this if you put patch 4/5 before this one. With this:

This patch will get backported to the stable kernels. Patch 4 on the
other hand does not.

> Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
>
> > +       /*
> > +        * If any of the affected OTP regions are locked the entire 
> > range is
> > +        * considered locked.
> > +        */
> > +       for (region = spi_nor_otp_offset_to_region(nor, ofs);
> > +            region <= spi_nor_otp_offset_to_region(nor, ofs + len - 
> > 1);
> > +            region++) {
> > +               locked = ops->is_locked(nor, region);
> > +               /* take the branch it is locked or in case of an error 
> > */
> > +               if (locked)
> > +                       return locked;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> >  static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t 
> > ofs,
> >                                       size_t total_len, size_t 
> > *retlen,
> >                                       const u8 *buf, bool is_write)
> > @@ -271,6 +297,16 @@ static int spi_nor_mtd_otp_read_write(struct 
> > mtd_info *mtd, loff_t ofs,
> >         /* don't access beyond the end */
> >         total_len = min_t(size_t, total_len, spi_nor_otp_size(nor) - 
> > ofs);
> >
> > +       if (is_write) {
> > +               ret = spi_nor_mtd_otp_range_is_locked(nor, ofs, 
> > total_len);
> > +               if (ret < 0) {
> > +                       goto out;
> > +               } else if (ret) {
> > +                       ret = -EROFS;
> > +                       goto out;
> > +               }
> > +       }
> > +
> >         *retlen = 0;
> >         while (total_len) {
> >                 /*
> > --
> > 2.20.1