Re: [Qemu-devel] [PATCH] smbus_eeprom: Limit data writes to 255 bytes

[Philippe Mathieu-Daudé]

Hi Michael,

On Thu, Dec 27, 2018 at 12:53 PM Michael Hanselmann <address@hidden> wrote:
&gt; The "eeprom_write_data" function in "smbus_eeprom.c" had no provisions
&gt; to limit the length of data written. If a caller were able to manipulate
&gt; the "len" parameter they could potentially write before or after the
&gt; target buffer.

You forgot to sign your commit:
"Signed-off-by: Michael Hanselmann <address@hidden>"

(See 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/SubmittingPatches?id=f6f94e2ab1b33f0082ac22d71f66385a60d8157f#n297)

> ---
>  hw/i2c/smbus_eeprom.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/hw/i2c/smbus_eeprom.c b/hw/i2c/smbus_eeprom.c
> index f18aa3de35..74fa1c328c 100644
> --- a/hw/i2c/smbus_eeprom.c
> +++ b/hw/i2c/smbus_eeprom.c
> @@ -76,6 +76,7 @@ static void eeprom_write_data(SMBusDevice *dev, uint8_t 
> cmd, uint8_t *buf, int l
>         It is a block write without a length byte.  Fortunately we
>         get the full block anyway.  */
>      /* TODO: Should this set the current location?  */
> +    len &= 0xff;
>      if (cmd + len > 256)

Corey Minyard sent a cleanup series [1] because this device model is
known to be unsafe and need rewrite.
There is a particular patch [2] which add the SMBUS_EEPROM_SIZE definition.
He also provided a intent at cleaning this problem here [3] where
Peter suggested to split it in fewer patches.

Regards,

Phil.

[1] https://lists.gnu.org/archive/html/qemu-devel/2018-11/msg05293.html
[2] https://lists.gnu.org/archive/html/qemu-devel/2018-11/msg05295.html
[3] https://lists.gnu.org/archive/html/qemu-devel/2018-11/msg05298.html

>          n = 256 - cmd;
>      else
> --
> 2.11.0
>
>