Re: [PATCH] fix CONFIG_IO_STRICT_DEVMEM, do not enable by default

[Kees Cook]

On Wed, Jan 20, 2016 at 2:37 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> Larry reports: "My PowerBook G4 Aluminum with a 32-bit PPC processor
> fails to boot for the 4.4-git series".  This is likely due to X still
> needing /dev/mem access on this platform.
>
> CONFIG_IO_STRICT_DEVMEM is not yet safe to turn on when
> CONFIG_STRICT_DEVMEM=y.  Remove the default so that old configurations
> do not change behavior.
>
> Fixes: 90a545e98126 ("restrict /dev/mem to idle io memory ranges")
> Reported-by: Larry Finger <Larry.Finger@xxxxxxxxxxxx>
> Tested-by: Larry Finger <Larry.Finger@xxxxxxxxxxxx>
> Link: http://marc.info/?l=linux-kernel&m=145332012023825&w=2
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>

Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>

This should probably be CC: stable, yes?

-Kees

> ---
>  lib/Kconfig.debug |    1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index f75a33f29f6e..7d0b49c536c5 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -1919,7 +1919,6 @@ config STRICT_DEVMEM
>  config IO_STRICT_DEVMEM
>         bool "Filter I/O access to /dev/mem"
>         depends on STRICT_DEVMEM
> -       default STRICT_DEVMEM
>         ---help---
>           If this option is disabled, you allow userspace (root) access to all
>           io-memory regardless of whether a driver is actively using that
>



-- 
Kees Cook
Chrome OS & Brillo Security