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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>
This commit is contained in:
Vasily Gorbik 2019-08-13 19:23:51 +02:00
parent 8769f610fe
commit 2c7fa8a11c
1 changed files with 2 additions and 2 deletions
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4
arch/s390/kernel/process.c
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@ -196,12 +196,12 @@ unsigned long get_wchan(struct task_struct *p)
goto out;
}
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) {
return_address = 0;
goto out;
}
return_address = sf->gprs[8];
return_address = READ_ONCE_NOCHECK(sf->gprs[8]);
if (!in_sched_functions(return_address))
goto out;
}