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    Subject[PATCH 4/6] freezer: use lock_task_sighand() in fake_signal_wake_up()
    Date
    cgroup_freezer calls freeze_task() without holding tasklist_lock and,
    if the task is exiting, its ->sighand may be gone by the time
    fake_signal_wake_up() is called. Use lock_task_sighand() instead of
    accessing ->sighand directly.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Reported-by: Oleg Nesterov <oleg@redhat.com>
    Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
    Cc: Paul Menage <paul@paulmenage.org>
    ---
    kernel/freezer.c | 7 ++++---
    1 files changed, 4 insertions(+), 3 deletions(-)
    diff --git a/kernel/freezer.c b/kernel/freezer.c
    index ebee1ab..9846133 100644
    --- a/kernel/freezer.c
    +++ b/kernel/freezer.c
    @@ -93,9 +93,10 @@ static void fake_signal_wake_up(struct task_struct *p)
    {
    unsigned long flags;

    - spin_lock_irqsave(&p->sighand->siglock, flags);
    - signal_wake_up(p, 0);
    - spin_unlock_irqrestore(&p->sighand->siglock, flags);
    + if (lock_task_sighand(p, &flags)) {
    + signal_wake_up(p, 0);
    + unlock_task_sighand(p, &flags);
    + }
    }

    /**
    --
    1.7.6


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