Commit f7d27c35 authored Oct 19, 2015 by Andrey Ryabinin Committed by Ingo Molnar Oct 20, 2015

x86/mm, kasan: Silence KASAN warnings in get_wchan()



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>

parent d976441f

arch/x86/kernel/process.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -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;
		}