[patch 4/5] -fstack-protector feature: Add the __stack_chk_fail() function

[Arjan van de Ven <arjan@linux.intel.com>]

Subject: [patch 4/5] Add the __stack_chk_fail() function

GCC emits a call to a __stack_chk_fail() function when the stack canary is
not matching the expected value.

Since this is a bad security issue; lets panic the kernel rather than limping
along; the kernel really can't be trusted anymore when this happens.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
CC: Andi Kleen <ak@suse.de>

---
 kernel/panic.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

Index: linux-2.6.18-rc4-stackprot/kernel/panic.c
===================================================================
--- linux-2.6.18-rc4-stackprot.orig/kernel/panic.c
+++ linux-2.6.18-rc4-stackprot/kernel/panic.c
@@ -269,3 +269,15 @@ void oops_exit(void)
 {
 	do_oops_enter_exit();
 }
+
+#ifdef CONFIG_CC_STACKPROTECTOR
+/*
+ * Called when gcc's -fstack-protector feature is used, and
+ * gcc detects corruption of the on-stack canary value
+ */
+void __stack_chk_fail(void)
+{
+	panic("stack-protector: Kernel stack is corrupted");
+}
+EXPORT_SYMBOL(__stack_chk_fail);
+#endif