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Date: Thu, 2 Feb 2017 08:23:31 -0800
From: Kees Cook <keescook@...omium.org>
To: Keun-O Park <kpark3469@...il.com>
Cc: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>,
Mark Rutland <mark.rutland@....com>, James Morse <james.morse@....com>,
Pratyush Anand <panand@...hat.com>, keun-o.park@...kmatter.ae
Subject: Re: [PATCH v2 1/3] usercopy: create usercopy.h and move enum stack_type
On Thu, Feb 2, 2017 at 4:50 AM, <kpark3469@...il.com> wrote:
> From: Sahara <keun-o.park@...kmatter.ae>
>
> This patch creates linux/usercopy.h and moves the enum which is
> only used in usercopy.c so as to make it usable to x86 and other
> architecture's thread_info.h, which may have arch_within_stack_frames().
Yeah, I had meant to do this; thanks! See my nit below...
> Signed-off-by: Sahara <keun-o.park@...kmatter.ae>
> Suggested-by: James Morse <james.morse@....com>
> ---
> arch/x86/include/asm/thread_info.h | 20 +++++++++++---------
> include/linux/usercopy.h | 11 +++++++++++
> mm/usercopy.c | 8 +-------
> 3 files changed, 23 insertions(+), 16 deletions(-)
> create mode 100644 include/linux/usercopy.h
>
> diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
> index ad6f5eb0..c991126 100644
> --- a/arch/x86/include/asm/thread_info.h
> +++ b/arch/x86/include/asm/thread_info.h
> @@ -51,6 +51,7 @@
> struct task_struct;
> #include <asm/cpufeature.h>
> #include <linux/atomic.h>
> +#include <linux/usercopy.h>
>
> struct thread_info {
> unsigned long flags; /* low level flags */
> @@ -168,13 +169,13 @@ 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 +198,14 @@ 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/usercopy.h b/include/linux/usercopy.h
> new file mode 100644
> index 0000000..974859e
> --- /dev/null
> +++ b/include/linux/usercopy.h
> @@ -0,0 +1,11 @@
> +#ifndef __LINUX_USERCOPY_H
> +#define __LINUX_USERCOPY_H
> +
> +enum stack_type {
> + BAD_STACK = -1,
> + NOT_STACK = 0,
> + GOOD_FRAME,
> + GOOD_STACK,
> +};
> +
> +#endif
I think this should live with the declaration of
arch_within_stack_frames in include/linux/thread_info.h instead of
creating a new usercopy.h.
-Kees
> diff --git a/mm/usercopy.c b/mm/usercopy.c
> index 3c8da0a..ee7bced 100644
> --- a/mm/usercopy.c
> +++ b/mm/usercopy.c
> @@ -16,15 +16,9 @@
>
> #include <linux/mm.h>
> #include <linux/slab.h>
> +#include <linux/usercopy.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
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