Re: [PATCH] Kconfig: Make config Filter access to /dev/mem default y

[Xiaotian Feng]

On Tue, Apr 13, 2010 at 10:52 AM,  <wzt.wzt@xxxxxxxxx> wrote:
> Recently, most company start use >=2.6.31 kernels to replace redhat kernels.
> But the config "Filter access to /dev/mem" is "default n", that allows kernel
> rootkit using /dev/mem again. it could access all kernel memory default. Most
> administrator don't known the "Filter access to /dev/mem" is "defult N", when
> he compiles the kernel, it's easily to be attacked by rootkit.

Have you ever successfully attack by this way? If CONFIG_STRICT_DEVMEM
is not set, the /dev/mem access is filtered in pat code.

>
> Signed-off-by: Zhitong Wang <zhitong.wangzt@xxxxxxxxxxxxxxx>
>
> ---
> Âarch/x86/Kconfig.debug      Â|  Â3 ++-
> Âarch/x86/configs/i386_defconfig  |  Â2 +-
> Âarch/x86/configs/x86_64_defconfig | Â Â2 +-
> Â3 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
> index bc01e3e..733aea6 100644
> --- a/arch/x86/Kconfig.debug
> +++ b/arch/x86/Kconfig.debug
> @@ -7,6 +7,7 @@ source "lib/Kconfig.debug"
>
> Âconfig STRICT_DEVMEM
> Â Â Â Âbool "Filter access to /dev/mem"
> + Â Â Â default y
> Â Â Â Â---help---
> Â Â Â Â ÂIf this option is disabled, you allow userspace (root) access to all
> Â Â Â Â Âof memory, including kernel and userspace memory. Accidental
> @@ -20,7 +21,7 @@ config STRICT_DEVMEM
> Â Â Â Â ÂThis is sufficient for dosemu and X and all common users of
> Â Â Â Â Â/dev/mem.
>
> - Â Â Â Â If in doubt, say Y.
> + Â Â Â Â If in doubt, say N.
>
> Âconfig X86_VERBOSE_BOOTUP
> Â Â Â Âbool "Enable verbose x86 bootup info messages"
> diff --git a/arch/x86/configs/i386_defconfig b/arch/x86/configs/i386_defconfig
> index d28fad1..95c85a8 100644
> --- a/arch/x86/configs/i386_defconfig
> +++ b/arch/x86/configs/i386_defconfig
> @@ -2386,7 +2386,7 @@ CONFIG_PROVIDE_OHCI1394_DMA_INIT=y
> Â# CONFIG_SAMPLES is not set
> ÂCONFIG_HAVE_ARCH_KGDB=y
> Â# CONFIG_KGDB is not set
> -# CONFIG_STRICT_DEVMEM is not set
> +CONFIG_STRICT_DEVMEM=y
> ÂCONFIG_X86_VERBOSE_BOOTUP=y
> ÂCONFIG_EARLY_PRINTK=y
> ÂCONFIG_EARLY_PRINTK_DBGP=y
> diff --git a/arch/x86/configs/x86_64_defconfig b/arch/x86/configs/x86_64_defconfig
> index 6c86acd..659bfe7 100644
> --- a/arch/x86/configs/x86_64_defconfig
> +++ b/arch/x86/configs/x86_64_defconfig
> @@ -2360,7 +2360,7 @@ CONFIG_PROVIDE_OHCI1394_DMA_INIT=y
> Â# CONFIG_SAMPLES is not set
> ÂCONFIG_HAVE_ARCH_KGDB=y
> Â# CONFIG_KGDB is not set
> -# CONFIG_STRICT_DEVMEM is not set
> +CONFIG_STRICT_DEVMEM=y
> ÂCONFIG_X86_VERBOSE_BOOTUP=y
> ÂCONFIG_EARLY_PRINTK=y
> ÂCONFIG_EARLY_PRINTK_DBGP=y
> --
> 1.6.5.3
>
> --
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