[kernel-hardening] Re: [PATCH v3 1/3] usercopy: create enum stack_type

Kees Cook
2017-02-06T22:23:09Z

On Sun, Feb 5, 2017 at 4:14 AM, <kpark3469@gmail.com> wrote:
> From: Sahara <keun-o.park@darkmatter.ae>
>
> This patch creates enum stack_type which is only used in usercopy.c
> for now. This enum type can be used for x86 and other architecture's
> thread_info.h, which may have arch_within_stack_frames().
>
> Signed-off-by: Sahara <keun-o.park@darkmatter.ae>
> Suggested-by: James Morse <james.morse@arm.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>

Acked-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
> arch/x86/include/asm/thread_info.h | 19 ++++++++++---------
> include/linux/thread_info.h | 13 ++++++++++---
> mm/usercopy.c | 8 +-------
> 3 files changed, 21 insertions(+), 19 deletions(-)
>
> diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
> index ad6f5eb0..7af4b8b 100644
> --- a/arch/x86/include/asm/thread_info.h
> +++ b/arch/x86/include/asm/thread_info.h
> @@ -168,13 +168,13 @@ static inline unsigned long current_stack_pointer(void)
> * entirely contained by a single stack frame.
> *
> * Returns:
> - * 1 if within a frame
> - * -1 if placed across a frame boundary (or outside stack)
> - * 0 unable to determine (no frame pointers, etc)
> + * GOOD_FRAME if within a frame
> + * BAD_STACK if placed across a frame boundary (or outside stack)
> + * NOT_STACK unable to determine (no frame pointers, etc)
> */
> -static inline int arch_within_stack_frames(const void * const stack,
> - const void * const stackend,
> - const void *obj, unsigned long len)
> +static inline enum stack_type arch_within_stack_frames(const void * const stack,
> + const void * const stackend,
> + const void *obj, unsigned long len)
> {
> #if defined(CONFIG_FRAME_POINTER)
> const void *frame = NULL;
> @@ -197,13 +197,14 @@ static inline int arch_within_stack_frames(const void * const stack,
> * the copy as invalid.
> */
> if (obj + len <= frame)
> - return obj >= oldframe + 2 * sizeof(void *) ? 1 : -1;
> + return obj >= oldframe + 2 * sizeof(void *) ?
> + GOOD_FRAME : BAD_STACK;
> oldframe = frame;
> frame = *(const void * const *)frame;
> }
> - return -1;
> + return BAD_STACK;
> #else
> - return 0;
> + return NOT_STACK;
> #endif
> }
>
> diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
> index 5837387..a38b3be 100644
> --- a/include/linux/thread_info.h
> +++ b/include/linux/thread_info.h
> @@ -22,6 +22,13 @@
> #endif
>
> #include <linux/bitops.h>
> +
> +enum stack_type {
> + BAD_STACK = -1,
> + NOT_STACK = 0,
> + GOOD_FRAME,
> + GOOD_STACK,
> +};
> #include <asm/thread_info.h>
>
> #ifdef __KERNEL__
> @@ -77,9 +84,9 @@ static inline int test_ti_thread_flag(struct thread_info *ti, int flag)
> #define tif_need_resched() test_thread_flag(TIF_NEED_RESCHED)
>
> #ifndef CONFIG_HAVE_ARCH_WITHIN_STACK_FRAMES
> -static inline int arch_within_stack_frames(const void * const stack,
> - const void * const stackend,
> - const void *obj, unsigned long len)
> +static inline enum stack_type arch_within_stack_frames(const void * const stack,
> + const void * const stackend,
> + const void *obj, unsigned long len)
> {
> return 0;
> }
> diff --git a/mm/usercopy.c b/mm/usercopy.c
> index 3c8da0a..3531ae7 100644
> --- a/mm/usercopy.c
> +++ b/mm/usercopy.c
> @@ -16,15 +16,9 @@
>
> #include <linux/mm.h>
> #include <linux/slab.h>
> +#include <linux/thread_info.h>
> #include <asm/sections.h>
>
> -enum {
> - BAD_STACK = -1,
> - NOT_STACK = 0,
> - GOOD_FRAME,
> - GOOD_STACK,
> -};
> -
> /*
> * Checks if a given pointer and length is contained by the current
> * stack frame (if possible).
> --
> 2.7.4
>

--
Kees Cook
Pixel Security