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

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

[Kees Cook]

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@chromium.org>
---
 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

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

[Andrey Smirnov]

On Wed, Jun 20, 2018 at 11:26 AM Kees Cook <keescook@chromium.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@chromium.org>

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

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