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

kpark3469
2017-02-05T12:14:08Z

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>
---
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