linux-kernel - [patch 4/5] Add the __stack_chk

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Date:	Fri, 28 Jul 2006 18:05:05 +0200
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...l.org, ak@...e.de
Subject: [patch 4/5] Add the __stack_chk_fail() function

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@...ux.intel.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
CC: Andi Kleen <ak@...e.de>

Index: linux-2.6.18-rc2-git5-stackprot/kernel/panic.c
===================================================================
--- linux-2.6.18-rc2-git5-stackprot.orig/kernel/panic.c
+++ linux-2.6.18-rc2-git5-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

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