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sched/kasan: remove stale KASAN poison after hotplug

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Functions which the compiler has instrumented for KASAN place poison on
the stack shadow upon entry and remove this poision prior to returning.

In the case of CPU hotplug, CPUs exit the kernel a number of levels deep
in C code.  Any instrumented functions on this critical path will leave
portions of the stack shadow poisoned.

When a CPU is subsequently brought back into the kernel via a different
path, depending on stackframe, layout calls to instrumented functions
may hit this stale poison, resulting in (spurious) KASAN splats to the
console.

To avoid this, clear any stale poison from the idle thread for a CPU
prior to bringing a CPU online.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mark Rutland 2016-03-09 14:08:18 -08:00 committed by Linus Torvalds
parent e3ae116339
commit e1b77c9298
1 changed files with 3 additions and 0 deletions
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3
kernel/sched/core.c
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@ -26,6 +26,7 @@
* Thomas Gleixner, Mike Kravetz
*/
#include <linux/kasan.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/nmi.h>
@ -5096,6 +5097,8 @@ void init_idle(struct task_struct *idle, int cpu)
idle->state = TASK_RUNNING;
idle->se.exec_start = sched_clock();
kasan_unpoison_task_stack(idle);
#ifdef CONFIG_SMP
/*
* Its possible that init_idle() gets called multiple times on a task,