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From:   Qianli Zhao <zhaoqianligood@gmail.com>
To:     tglx@linutronix.de, john.stultz@linaro.org, sboyd@kernel.org
Cc:     linux-kernel@vger.kernel.org, zhaoqianli@xiaomi.com
Subject: [PATCH] timer: mask unnecessary set of flags in do_init_timer
Date:   Fri,  7 Aug 2020 10:29:38 +0800
Message-Id: <1596767378-27241-1-git-send-email-zhaoqianligood@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Qianli Zhao <zhaoqianli@xiaomi.com>

do_init_timer can specify flags of timer_list,
but this function does not expect to specify the CPU or idx.
If user invoking do_init_timer and specify CPU,
The result may not what we expected.

E.g:
do_init_timer invoked in core2,and specify flags 0x1
final result flags is 0x3.If the specified CPU number
exceeds the actual number,more serious problems will happen

Signed-off-by: Qianli Zhao <zhaoqianli@xiaomi.com>
---
 kernel/time/timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 026ac01..17e3737 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -789,7 +789,7 @@ static void do_init_timer(struct timer_list *timer,
 {
 	timer->entry.pprev = NULL;
 	timer->function = func;
-	timer->flags = flags | raw_smp_processor_id();
+	timer->flags = (flags & ~TIMER_BASEMASK & ~TIMER_ARRAYMASK) | raw_smp_processor_id();
 	lockdep_init_map(&timer->lockdep_map, name, key, 0);
 }
 
-- 
2.7.4