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    SubjectRe: [PATCH] Kconfig: Make config Filter access to /dev/mem default y
    From
    On Tue, Apr 13, 2010 at 10:52 AM,  <wzt.wzt@gmail.com> 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@alibaba-inc.com>
    >
    > ---
    >  arch/x86/Kconfig.debug            |    3 ++-
    >  arch/x86/configs/i386_defconfig   |    2 +-
    >  arch/x86/configs/x86_64_defconfig |    2 +-
    >  3 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"
    >
    >  config STRICT_DEVMEM
    >        bool "Filter access to /dev/mem"
    > +       default y
    >        ---help---
    >          If this option is disabled, you allow userspace (root) access to all
    >          of memory, including kernel and userspace memory. Accidental
    > @@ -20,7 +21,7 @@ config STRICT_DEVMEM
    >          This is sufficient for dosemu and X and all common users of
    >          /dev/mem.
    >
    > -         If in doubt, say Y.
    > +         If in doubt, say N.
    >
    >  config X86_VERBOSE_BOOTUP
    >        bool "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
    >  # CONFIG_SAMPLES is not set
    >  CONFIG_HAVE_ARCH_KGDB=y
    >  # CONFIG_KGDB is not set
    > -# CONFIG_STRICT_DEVMEM is not set
    > +CONFIG_STRICT_DEVMEM=y
    >  CONFIG_X86_VERBOSE_BOOTUP=y
    >  CONFIG_EARLY_PRINTK=y
    >  CONFIG_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
    >  # CONFIG_SAMPLES is not set
    >  CONFIG_HAVE_ARCH_KGDB=y
    >  # CONFIG_KGDB is not set
    > -# CONFIG_STRICT_DEVMEM is not set
    > +CONFIG_STRICT_DEVMEM=y
    >  CONFIG_X86_VERBOSE_BOOTUP=y
    >  CONFIG_EARLY_PRINTK=y
    >  CONFIG_EARLY_PRINTK_DBGP=y
    > --
    > 1.6.5.3
    >
    > --
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