Commit 2c7fa8a1 authored Aug 13, 2019 by Vasily Gorbik

s390/kasan: avoid report in get_wchan

Reading other running task's stack can be a dangerous endeavor. Kasan
stack memory access instrumentation includes special prologue and epilogue
to mark/remove red zones in shadow memory between stack variables. For
that reason there is always a race between a task reading value in other
task's stack and that other task returning from a function and entering
another one generating different red zones pattern.

To avoid kasan reports simply perform uninstrumented memory reads.

Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

parent 8769f610

arch/s390/kernel/process.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -196,12 +196,12 @@ unsigned long get_wchan(struct task_struct *p)
	goto out;		goto out;
	}		}
	for (count = 0; count < 16; count++) {		for (count = 0; count < 16; count++) {
	sf = (struct stack_frame *) sf->back_chain;		sf = (struct stack_frame *)READ_ONCE_NOCHECK(sf->back_chain);
	if (sf <= low \|\| sf > high) {		if (sf <= low \|\| sf > high) {
	return_address = 0;		return_address = 0;
	goto out;		goto out;
	}		}
	return_address = sf->gprs[8];		return_address = READ_ONCE_NOCHECK(sf->gprs[8]);
	if (!in_sched_functions(return_address))		if (!in_sched_functions(return_address))
	goto out;		goto out;
	}		}