From: Sven Schnelle svens@linux.ibm.com
[ Upstream commit 6feeee8efc53035c3195b02068b58ae947538aa4 ]
The following sequence triggers a kernel stack overflow on s390x:
mount -t tracefs tracefs /sys/kernel/tracing cd /sys/kernel/tracing echo function_graph > current_tracer [crash]
This is because preempt_count_{add,sub} are in the list of traced functions, which can be demonstrated by:
echo preempt_count_add >set_ftrace_filter echo function_graph > current_tracer [crash]
The stack overflow happens because get_tod_clock_monotonic() gets called by ftrace but itself calls preempt_{disable,enable}(), which leads to a endless recursion. Fix this by using preempt_{disable,enable}_notrace().
Fixes: 011620688a71 ("s390/time: ensure get_clock_monotonic() returns monotonic values") Signed-off-by: Sven Schnelle svens@linux.ibm.com Reviewed-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- arch/s390/include/asm/timex.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/s390/include/asm/timex.h b/arch/s390/include/asm/timex.h index 0f12a3f..2dc9eb4 100644 --- a/arch/s390/include/asm/timex.h +++ b/arch/s390/include/asm/timex.h @@ -195,9 +195,9 @@ static inline unsigned long long get_tod_clock_monotonic(void) { unsigned long long tod;
- preempt_disable(); + preempt_disable_notrace(); tod = get_tod_clock() - *(unsigned long long *) &tod_clock_base[1]; - preempt_enable(); + preempt_enable_notrace(); return tod; }