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x86/mm, kasan: Silence KASAN warnings in get_wchan()
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get_wchan() is racy by design, it may access volatile stack
of running task, thus it may access redzone in a stack frame
and cause KASAN to warn about this.

Use READ_ONCE_NOCHECK() to silence these warnings.

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wolfram Gloger <wmglo@dent.med.uni-muenchen.de>
Cc: kasan-dev <kasan-dev@googlegroups.com>
Link: http://lkml.kernel.org/r/1445243838-17763-3-git-send-email-aryabinin@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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aryabinin authored and Ingo Molnar committed Oct 20, 2015
1 parent d976441 commit f7d27c3
Showing 1 changed file with 3 additions and 3 deletions.
6 changes: 3 additions & 3 deletions arch/x86/kernel/process.c
Original file line number Diff line number Diff line change
Expand Up @@ -550,14 +550,14 @@ unsigned long get_wchan(struct task_struct *p)
if (sp < bottom || sp > top)
return 0;

fp = READ_ONCE(*(unsigned long *)sp);
fp = READ_ONCE_NOCHECK(*(unsigned long *)sp);
do {
if (fp < bottom || fp > top)
return 0;
ip = READ_ONCE(*(unsigned long *)(fp + sizeof(unsigned long)));
ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long)));
if (!in_sched_functions(ip))
return ip;
fp = READ_ONCE(*(unsigned long *)fp);
fp = READ_ONCE_NOCHECK(*(unsigned long *)fp);
} while (count++ < 16 && p->state != TASK_RUNNING);
return 0;
}

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