Add correct address for linux-mm
On 06/25/2018 11:08 AM, Chris von Recklinghausen wrote:
> Enabling HARDENED_USER_COPY causes measurable regressions in the
> networking performances, up to 8% under UDP flood.
>
> A generic distro may want to enable HARDENED_USER_COPY in their default
> kernel config, but at the same time, such distro may want to be able to
> avoid the performance penalties in with the default configuration and
> enable the stricter check on a per-boot basis.
>
> This change adds a config variable and a boot parameter to conditionally
> enable HARDENED_USER_COPY at boot time, and switch HUC to off if
> HUC_DEFAULT_OFF is set.
>
> Signed-off-by: Chris von Recklinghausen <crecklin@xxxxxxxxxx>
> ---
> .../admin-guide/kernel-parameters.rst | 2 ++
> .../admin-guide/kernel-parameters.txt | 3 ++
> include/linux/thread_info.h | 7 +++++
> mm/usercopy.c | 28 +++++++++++++++++++
> security/Kconfig | 10 +++++++
> 5 files changed, 50 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
> index b8d0bc07ed0a..c3035038e3ae 100644
> --- a/Documentation/admin-guide/kernel-parameters.rst
> +++ b/Documentation/admin-guide/kernel-parameters.rst
> @@ -100,6 +100,8 @@ parameter is applicable::
> FB The frame buffer device is enabled.
> FTRACE Function tracing enabled.
> GCOV GCOV profiling is enabled.
> + HUC Hardened usercopy is enabled
> + HUCF Hardened usercopy disabled at boot
> HW Appropriate hardware is enabled.
> IA-64 IA-64 architecture is enabled.
> IMA Integrity measurement architecture is enabled.
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index efc7aa7a0670..cd3354bc14d3 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -816,6 +816,9 @@
> disable= [IPV6]
> See Documentation/networking/ipv6.txt.
>
> + enable_hardened_usercopy [HUC,HUCF]
> + Enable hardened usercopy checks
> +
> disable_radix [PPC]
> Disable RADIX MMU mode on POWER9
>
> diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
> index 8d8821b3689a..140a36cc1c2c 100644
> --- a/include/linux/thread_info.h
> +++ b/include/linux/thread_info.h
> @@ -109,12 +109,19 @@ static inline int arch_within_stack_frames(const void * const stack,
> #endif
>
> #ifdef CONFIG_HARDENED_USERCOPY
> +#include <linux/jump_label.h>
> +
> +DECLARE_STATIC_KEY_FALSE(bypass_usercopy_checks);
> +
> extern void __check_object_size(const void *ptr, unsigned long n,
> bool to_user);
>
> static __always_inline void check_object_size(const void *ptr, unsigned long n,
> bool to_user)
> {
> + if (static_branch_likely(&bypass_usercopy_checks))
> + return;
> +
> if (!__builtin_constant_p(n))
> __check_object_size(ptr, n, to_user);
> }
> diff --git a/mm/usercopy.c b/mm/usercopy.c
> index e9e9325f7638..ce3996da1b2e 100644
> --- a/mm/usercopy.c
> +++ b/mm/usercopy.c
> @@ -279,3 +279,31 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user)
> check_kernel_text_object((const unsigned long)ptr, n, to_user);
> }
> EXPORT_SYMBOL(__check_object_size);
> +
> +DEFINE_STATIC_KEY_FALSE(bypass_usercopy_checks);
> +EXPORT_SYMBOL(bypass_usercopy_checks);
> +
> +#ifdef CONFIG_HUC_DEFAULT_OFF
> +#define HUC_DEFAULT false
> +#else
> +#define HUC_DEFAULT true
> +#endif
> +
> +static bool enable_huc_atboot = HUC_DEFAULT;
> +
> +static int __init parse_enable_usercopy(char *str)
> +{
> + enable_huc_atboot = true;
> + return 1;
> +}
> +
> +static int __init set_enable_usercopy(void)
> +{
> + if (enable_huc_atboot == false)
> + static_branch_enable(&bypass_usercopy_checks);
> + return 1;
> +}
> +
> +__setup("enable_hardened_usercopy", parse_enable_usercopy);
> +
> +late_initcall(set_enable_usercopy);
> diff --git a/security/Kconfig b/security/Kconfig
> index c4302067a3ad..a6173897b85c 100644
> --- a/security/Kconfig
> +++ b/security/Kconfig
> @@ -189,6 +189,16 @@ config HARDENED_USERCOPY_PAGESPAN
> been removed. This config is intended to be used only while
> trying to find such users.
>
> +config HUC_DEFAULT_OFF
> + bool "allow CONFIG_HARDENED_USERCOPY to be configured but disabled"
> + depends on HARDENED_USERCOPY
> + help
> + When CONFIG_HARDENED_USERCOPY is enabled, disable its
> + functionality unless it is enabled via at boot time
> + via the "enable_hardened_usercopy" boot parameter. This allows
> + the functionality of hardened usercopy to be present but not
> + impact performance unless it is needed.
> +
> config FORTIFY_SOURCE
> bool "Harden common str/mem functions against buffer overflows"
> depends on ARCH_HAS_FORTIFY_SOURCE
