From: Arjan van de Ven <arjan@linux.intel.com>
Date: Fri, 11 Jul 2008 12:09:55 +0000 (-0700)
Subject: stackprotector: better self-test
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=aa92db14270b79f0f91a9060b547a46f9e2639da;p=deliverable%2Flinux.git

stackprotector: better self-test

check stackprotector functionality by manipulating the canary briefly
during bootup.

far more robust than trying to overflow the stack. (which is architecture
dependent, etc.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/kernel/panic.c b/kernel/panic.c
index 6729e3f4ebcb..28153aec7100 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -347,22 +347,18 @@ static noinline void __stack_chk_test_func(void)
 	if ((unsigned long)__builtin_return_address(0) ==
 					*(((unsigned long *)&foo)+1)) {
 		printk(KERN_ERR "No -fstack-protector-stack-frame!\n");
-		return;
 	}
 #ifdef CONFIG_FRAME_POINTER
 	/* We also don't want to clobber the frame pointer */
 	if ((unsigned long)__builtin_return_address(0) ==
 					*(((unsigned long *)&foo)+2)) {
 		printk(KERN_ERR "No -fstack-protector-stack-frame!\n");
-		return;
 	}
 #endif
-	barrier();
-	if (current->stack_canary == *(((unsigned long *)&foo)+1))
-		*(((unsigned long *)&foo)+1) = 0;
-	else
+	if (current->stack_canary != *(((unsigned long *)&foo)+1))
 		printk(KERN_ERR "No -fstack-protector canary found\n");
-	barrier();
+
+	current->stack_canary = ~current->stack_canary;
 }
 
 static int __stack_chk_test(void)
@@ -373,7 +369,8 @@ static int __stack_chk_test(void)
 	if (__stack_check_testing) {
 		printk(KERN_ERR "-fstack-protector-all test failed\n");
 		WARN_ON(1);
-	}
+	};
+	current->stack_canary = ~current->stack_canary;
 	return 0;
 }
 /*