usercopy: Move enum for arch_within_stack_frames()

This patch moves the arch_within_stack_frames() return value enum up in
the header files so that per-architecture implementations can reuse the
same return values.

Signed-off-by: Sahara <keun-o.park@darkmatter.ae>
Signed-off-by: James Morse <james.morse@arm.com>
[kees: adjusted naming and commit log]
Signed-off-by: Kees Cook <keescook@chromium.org>

3 files changed, 20 insertions, 13 deletions

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index ad6f5eb07a95..920ca1f7adea 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -168,9 +168,9 @@ 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,
@@ -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 58373875e8ee..0dbe41be6181 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -22,6 +22,18 @@
 #endif
 
 #include <linux/bitops.h>
+
+/*
+ * For per-arch arch_within_stack_frames() implementations, defined in
+ * asm/thread_info.h.
+ */
+enum {
+        BAD_STACK = -1,
+        NOT_STACK = 0,
+        GOOD_FRAME,
+        GOOD_STACK,
+};
+
 #include <asm/thread_info.h>
 
 #ifdef __KERNEL__
diff --git a/mm/usercopy.c b/mm/usercopy.c
index d155e12563b1..1eba99baf1cf 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -19,15 +19,9 @@
 #include <linux/sched.h>
 #include <linux/sched/task.h>
 #include <linux/sched/task_stack.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).