linux-kernel - Re: [PATCH] nvmem: rave-sp-eeprom: Remove VLA usage

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Message-ID: <CAHQ1cqF9so3TSHpLRvtUDtrxogse_dhVzs_H1MB+G=bB6GfA=A@mail.gmail.com>
Date:   Thu, 21 Jun 2018 06:19:13 -0700
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     keescook@...omium.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: Re: [PATCH] nvmem: rave-sp-eeprom: Remove VLA usage

On Wed, Jun 20, 2018 at 11:26 AM Kees Cook <keescook@...omium.org> wrote:
>
> In the quest to remove all stack VLA usage from the kernel[1], this
> uses the maximum allocation size for the stack and adds a sanity check,
> similar to what has already be done for the regular rave-sp driver.
>
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>
> Signed-off-by: Kees Cook <keescook@...omium.org>

I completely forgot that I was using VLAs in this driver. Thanks for
fixing that!

Reviewed-by: Andrey Smirnov <andrew.smirnov@...il.com>
Tested-by: Andrey Smirnov <andrew.smirnov@...il.com>

> ---
>  drivers/nvmem/rave-sp-eeprom.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvmem/rave-sp-eeprom.c b/drivers/nvmem/rave-sp-eeprom.c
> index 50aeea6ec6cc..66699d44f73d 100644
> --- a/drivers/nvmem/rave-sp-eeprom.c
> +++ b/drivers/nvmem/rave-sp-eeprom.c
> @@ -35,6 +35,7 @@ enum rave_sp_eeprom_header_size {
>         RAVE_SP_EEPROM_HEADER_SMALL = 4U,
>         RAVE_SP_EEPROM_HEADER_BIG   = 5U,
>  };
> +#define RAVE_SP_EEPROM_HEADER_MAX      RAVE_SP_EEPROM_HEADER_BIG
>
>  #define        RAVE_SP_EEPROM_PAGE_SIZE        32U
>
> @@ -97,9 +98,12 @@ static int rave_sp_eeprom_io(struct rave_sp_eeprom *eeprom,
>         const unsigned int rsp_size =
>                 is_write ? sizeof(*page) - sizeof(page->data) : sizeof(*page);
>         unsigned int offset = 0;
> -       u8 cmd[cmd_size];
> +       u8 cmd[RAVE_SP_EEPROM_HEADER_MAX + sizeof(page->data)];
>         int ret;
>
> +       if (WARN_ON(cmd_size > sizeof(cmd)))
> +               return -EINVAL;
> +
>         cmd[offset++] = eeprom->address;
>         cmd[offset++] = 0;
>         cmd[offset++] = type;
> --
> 2.17.1
>
>
> --
> Kees Cook
> Pixel Security