init/main.c: Give init_task a canary

Tasks get their end of stack set to STACK_END_MAGIC with the
aim to catch stack overruns. Currently this feature does not
apply to init_task. This patch removes this restriction.

Note that a similar patch was posted by Prarit Bhargava
some time ago but was never merged:

  http://marc.info/?l=linux-kernel&m=127144305403241&w=2

Signed-off-by: Aaron Tomlin <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Oleg Nesterov <[email protected]>
Acked-by: Michael Ellerman <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Alex Thorlton <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Daeseok Youn <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Fabian Frederick <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Michael Opdenacker <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Rusty Russell <[email protected]>
Cc: Seiji Aguchi <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Cc: Yasuaki Ishimatsu <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 82ff3d6efb19..118dca7d5a28 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -57,6 +57,7 @@ struct sched_param {
 #include <linux/llist.h>
 #include <linux/uidgid.h>
 #include <linux/gfp.h>
+#include <linux/magic.h>
 
 #include <asm/processor.h>
 
@@ -2638,6 +2639,7 @@ static inline unsigned long stack_not_used(struct task_struct *p)
 	return (unsigned long)n - (unsigned long)end_of_stack(p);
 }
 #endif
+extern void set_task_stack_end_magic(struct task_struct *tsk);
 
 /* set thread flags in other task's structures
  * - see asm/thread_info.h for TIF_xxxx flags available