From d7880812b3594d3c6dcbe3cfd71dabb17347d082 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 10 Jun 2013 16:52:03 +0200
Subject: idle: Add the stack canary init to cpu_startup_entry()
Moving x86 to the generic idle implementation (commit 7d1a9417 "x86:
Use generic idle loop") wreckaged the stack protector.
I stupidly missed that boot_init_stack_canary() must be inlined from a
function which never returns, but I put that call into
arch_cpu_idle_prepare() which of course returns.
I pondered to play tricks with arch_cpu_idle_prepare() first, but then
I noticed, that the other archs which have implemented the
stackprotector (ARM and SH) do not initialize the canary for the
non-boot cpus.
So I decided to move the boot_init_stack_canary() call into
cpu_startup_entry() ifdeffed with an CONFIG_X86 for now. This #ifdef
is just a temporary measure as I don't want to inflict the
boot_init_stack_canary() call on ARM and SH that late in the cycle.
I'll queue a patch for 3.11 which removes the #ifdef if the ARM/SH
maintainers have no objection.
Reported-by: Wouter van Kesteren <woutershep@gmail.com>
Cc: x86@kernel.org
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/cpu/idle.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
(limited to 'kernel')
diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c
index d5585f5e038e..bf2ee1aafa0e 100644
--- a/kernel/cpu/idle.c
+++ b/kernel/cpu/idle.c
@@ -5,6 +5,7 @@
#include <linux/cpu.h>
#include <linux/tick.h>
#include <linux/mm.h>
+#include <linux/stackprotector.h>
#include <asm/tlb.h>
@@ -112,6 +113,21 @@ static void cpu_idle_loop(void)
void cpu_startup_entry(enum cpuhp_state state)
{
+ /*
+ * This #ifdef needs to die, but it's too late in the cycle to
+ * make this generic (arm and sh have never invoked the canary
+ * init for the non boot cpus!). Will be fixed in 3.11
+ */
+#ifdef CONFIG_X86
+ /*
+ * If we're the non-boot CPU, nothing set the stack canary up
+ * for us. The boot CPU already has it initialized but no harm
+ * in doing it again. This is a good place for updating it, as
+ * we wont ever return from this function (so the invalid
+ * canaries already on the stack wont ever trigger).
+ */
+ boot_init_stack_canary();
+#endif
current_set_polling();
arch_cpu_idle_prepare();
cpu_idle_loop();
--
cgit