linux-kernel - [PATCH AUTOSEL 5.4 40/40] sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed

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Message-Id: <20200702012402.2701121-40-sashal@kernel.org>
Date:   Wed,  1 Jul 2020 21:24:01 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Scott Wood <swood@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.4 40/40] sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed_ptr(), to fix mask corruption

From: Scott Wood <swood@...hat.com>

[ Upstream commit fd844ba9ae59b51e34e77105d79f8eca780b3bd6 ]

This function is concerned with the long-term CPU mask, not the
transitory mask the task might have while migrate disabled.  Before
this patch, if a task was migrate-disabled at the time
__set_cpus_allowed_ptr() was called, and the new mask happened to be
equal to the CPU that the task was running on, then the mask update
would be lost.

Signed-off-by: Scott Wood <swood@...hat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lkml.kernel.org/r/20200617121742.cpxppyi7twxmpin7@linutronix.de
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 361cbc2dc9667..f5537f87c1928 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1649,7 +1649,7 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
 		goto out;
 	}
 
-	if (cpumask_equal(p->cpus_ptr, new_mask))
+	if (cpumask_equal(&p->cpus_mask, new_mask))
 		goto out;
 
 	dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask);
-- 
2.25.1