[PATCH 5/5] lkdtm: split atomic test into over and underflow

[Kees Cook]

Each direction of the atomic wrapping should be individually testable.

Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 drivers/misc/lkdtm_core.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c
index f212f865f9c6..b5a544f2b645 100644
--- a/drivers/misc/lkdtm_core.c
+++ b/drivers/misc/lkdtm_core.c
@@ -111,7 +111,8 @@ enum ctype {
        CT_WRITE_RO,
        CT_WRITE_RO_AFTER_INIT,
        CT_WRITE_KERN,
-       CT_WRAP_ATOMIC,
+       CT_ATOMIC_UNDERFLOW,
+       CT_ATOMIC_OVERFLOW,
        CT_USERCOPY_HEAP_SIZE_TO,
        CT_USERCOPY_HEAP_SIZE_FROM,
        CT_USERCOPY_HEAP_FLAG_TO,
@@ -160,7 +161,8 @@ static char* cp_type[] = {
        "WRITE_RO",
        "WRITE_RO_AFTER_INIT",
        "WRITE_KERN",
-       "WRAP_ATOMIC",
+       "ATOMIC_UNDERFLOW",
+       "ATOMIC_OVERFLOW",
        "USERCOPY_HEAP_SIZE_TO",
        "USERCOPY_HEAP_SIZE_FROM",
        "USERCOPY_HEAP_FLAG_TO",
@@ -894,13 +896,25 @@ static void lkdtm_do_action(enum ctype which)
                do_overwritten();
                break;
        }
-       case CT_WRAP_ATOMIC: {
+       case CT_ATOMIC_UNDERFLOW: {
                atomic_t under = ATOMIC_INIT(INT_MIN);
-               atomic_t over = ATOMIC_INIT(INT_MAX);
 
-               pr_info("attempting atomic underflow\n");
+               pr_info("attempting good atomic increment\n");
+               atomic_inc(&under);
+               atomic_dec(&under);
+
+               pr_info("attempting bad atomic underflow\n");
                atomic_dec(&under);
-               pr_info("attempting atomic overflow\n");
+               break;
+       }
+       case CT_ATOMIC_OVERFLOW: {
+               atomic_t over = ATOMIC_INIT(INT_MAX);
+
+               pr_info("attempting good atomic decrement\n");
+               atomic_dec(&over);
+               atomic_inc(&over);
+
+               pr_info("attempting bad atomic overflow\n");
                atomic_inc(&over);
 
                return;
-- 
2.7.4