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>

1 files changed, 5 insertions, 8 deletions

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;
 }
 /*