linux-kernel - Re: [PATCH v5 4/5] mtd: spi-nor: otp: simplify length check

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 4 Jun 2021 13:06:18 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <michael@...le.cc>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     <p.yadav@...com>, <miquel.raynal@...tlin.com>, <richard@....at>,
        <vigneshr@...com>
Subject: Re: [PATCH v5 4/5] mtd: spi-nor: otp: simplify length check

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
> 
> By moving the code around a bit, we can just check the length before
> calling spi_nor_mtd_otp_range_is_locked() and drop the length check
> there. This way we don't need to take the lock. This will also skip the
> "*retlen = 0" assignment if the length is zero. But mtdcore already does
> that for us. Thus we can drop that, too.
> 
> Signed-off-by: Michael Walle <michael@...le.cc>
> ---
>  drivers/mtd/spi-nor/otp.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/otp.c b/drivers/mtd/spi-nor/otp.c
> index 063f8fb68649..89fe52e3851a 100644
> --- a/drivers/mtd/spi-nor/otp.c
> +++ b/drivers/mtd/spi-nor/otp.c
> @@ -256,9 +256,6 @@ static int spi_nor_mtd_otp_range_is_locked(struct spi_nor *nor, loff_t ofs,
>         unsigned int region;
>         int locked;
> 
> -       if (!len)
> -               return 0;

these lines were just introduced in the previous patch. Can you please reorder 4 with 3,
so that we don't touch this twice? With that:

Reviewed-by: Tudor Ambarus <tudor.ambarus@...rochip.com>

> -
>         /*
>          * If any of the affected OTP regions are locked the entire range is
>          * considered locked.
> @@ -290,13 +287,16 @@ static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t ofs,
>         if (ofs < 0 || ofs >= spi_nor_otp_size(nor))
>                 return 0;
> 
> +       /* don't access beyond the end */
> +       total_len = min_t(size_t, total_len, spi_nor_otp_size(nor) - ofs);
> +
> +       if (!total_len)
> +               return 0;
> +
>         ret = spi_nor_lock_and_prep(nor);
>         if (ret)
>                 return ret;
> 
> -       /* 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) {
> @@ -307,7 +307,6 @@ static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t ofs,
>                 }
>         }
> 
> -       *retlen = 0;
>         while (total_len) {
>                 /*
>                  * The OTP regions are mapped into a contiguous area starting
> --
> 2.20.1
>