From 232f31ca12a94eb9f51182955285a4474f876af7 Mon Sep 17 00:00:00 2001
From: shyouhei <shyouhei@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Fri, 1 Feb 2019 07:26:39 +0000
Subject: on-smash canary detection

In addition to detect dead canary, we try to detect the very moment
when we smash the stack top.  Requested by k0kubun:
https://twitter.com/k0kubun/status/1085180749899194368


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66981 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 vm_insnhelper.h | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

(limited to 'vm_insnhelper.h')

diff --git a/vm_insnhelper.h b/vm_insnhelper.h
index b96c794d4f..c004e5ecd6 100644
--- a/vm_insnhelper.h
+++ b/vm_insnhelper.h
@@ -137,14 +137,22 @@ enum vm_regan_acttype {
 
 #if VM_CHECK_MODE > 0
 #define SETUP_CANARY() \
-    VALUE * canary; \
+    VALUE *canary; \
     if (leaf) { \
         canary = GET_SP(); \
         SET_SV(vm_stack_canary); \
+    } \
+    else {\
+        SET_SV(Qfalse); /* cleanup */ \
     }
 #define CHECK_CANARY() \
-    if (leaf && (*canary != vm_stack_canary)) { \
-        vm_canary_is_found_dead(INSN_ATTR(bin), *canary); \
+    if (leaf) { \
+        if (*canary == vm_stack_canary) { \
+            *canary = Qfalse; /* cleanup */ \
+        } \
+        else { \
+            vm_canary_is_found_dead(INSN_ATTR(bin), *canary); \
+        } \
     }
 #else
 #define SETUP_CANARY()          /* void */
-- 
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