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 6729e3f..28153ae 100644 (file)
--- 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;
 }
 /*