[PATCH v4 0/3] arm64: usercopy: Implement stack frame object validation

Hi all,

This version of Sahara's arch_within_stack_frames() series replaces the
open-coded stack walker with a call to arm64's existing walker.

Patch 2 can be tested independently with this change[0].

lkdtm's use of unallocated stack regions is a separate problem, patch 3
tries to address this.

Sahara, it would be good to get your review of this!
I'm afraid I omitted your patch-3 as it stopped the lkdtm test from working,
I suspect its not tricking the compiler, but I haven't investigated.


Thanks,

James

[0] Change to lkdtm to generate accesses that overlap stack frames.
--------------%<--------------

diff --git a/drivers/misc/lkdtm_usercopy.c b/drivers/misc/lkdtm_usercopy.c
index 1dd611423d8b..fcbba3a14387 100644
--- a/drivers/misc/lkdtm_usercopy.c
+++ b/drivers/misc/lkdtm_usercopy.c

@@ -57,7 +57,8 @@ static noinline void do_usercopy_stack(bool to_user, bool bad_frame)

        /* This is a pointer to outside our current stack frame. */
        if (bad_frame) {
-               bad_stack = do_usercopy_stack_callee((uintptr_t)&bad_stack);
+               bad_stack = __builtin_frame_address(0);
+               bad_stack -= sizeof(good_stack)/2;