mm: Implement stack frame object validation

This creates per-architecture function arch_within_stack_frames() that
should validate if a given object is contained by a kernel stack frame.
Initial implementation is on x86.

This is based on code from PaX.

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

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 15996290fed4..ef86cded5402 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -424,6 +424,15 @@ config CC_STACKPROTECTOR_STRONG
 
 endchoice
 
+config HAVE_ARCH_WITHIN_STACK_FRAMES
+        bool
+        help
+          An architecture should select this if it can walk the kernel stack
+          frames to determine if an object is part of either the arguments
+          or local variables (i.e. that it excludes saved return addresses,
+          and similar) by implementing an inline arch_within_stack_frames(),
+          which is used by CONFIG_HARDENED_USERCOPY.
+
 config HAVE_CONTEXT_TRACKING
         bool
         help