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>

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 4e7a37ff03ab9f6aba634be08f7650e1ef5f2f7c..81a5f5e8f142a867b56a5e335d1b2a6598a8fbbe 100644 (file)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -277,18 +277,6 @@ void exit_idle(void)
 }
 #endif
 
-void arch_cpu_idle_prepare(void)
-{
-       /*
-        * If we're the non-boot CPU, nothing set the stack canary up
-        * for us.  CPU0 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();
-}
-
 void arch_cpu_idle_enter(void)
 {
        local_touch_nmi();

diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c
index d5585f5e038ee1080f17777792a6927d5897e5ea..bf2ee1aafa0ef0e0859a9006cf51a51aa7150452 100644 (file)
--- 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();