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    Subject[PATCH 5.4 034/109] sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed_ptr(), to fix mask corruption
    Date
    From: Scott Wood <swood@redhat.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@redhat.com>
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Link: https://lkml.kernel.org/r/20200617121742.cpxppyi7twxmpin7@linutronix.de
    Signed-off-by: Sasha Levin <sashal@kernel.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 7238ef445dafb..8b3e99d095ae0 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


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