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    Subject[PATCH 6.0 041/862] fs: dlm: fix race between test_bit() and queue_work()
    Date
    From: Alexander Aring <aahringo@redhat.com>

    commit eef6ec9bf390e836a6c4029f3620fe49528aa1fe upstream.

    This patch fixes a race by using ls_cb_mutex around the bit
    operations and conditional code blocks for LSFL_CB_DELAY.

    The function dlm_callback_stop() expects to stop all callbacks and
    flush all currently queued onces. The set_bit() is not enough because
    there can still be queue_work() after the workqueue was flushed.
    To avoid queue_work() after set_bit(), surround both by ls_cb_mutex.

    Cc: stable@vger.kernel.org
    Signed-off-by: Alexander Aring <aahringo@redhat.com>
    Signed-off-by: David Teigland <teigland@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/dlm/ast.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    --- a/fs/dlm/ast.c
    +++ b/fs/dlm/ast.c
    @@ -200,13 +200,13 @@ void dlm_add_cb(struct dlm_lkb *lkb, uin
    if (!prev_seq) {
    kref_get(&lkb->lkb_ref);

    + mutex_lock(&ls->ls_cb_mutex);
    if (test_bit(LSFL_CB_DELAY, &ls->ls_flags)) {
    - mutex_lock(&ls->ls_cb_mutex);
    list_add(&lkb->lkb_cb_list, &ls->ls_cb_delay);
    - mutex_unlock(&ls->ls_cb_mutex);
    } else {
    queue_work(ls->ls_callback_wq, &lkb->lkb_cb_work);
    }
    + mutex_unlock(&ls->ls_cb_mutex);
    }
    out:
    mutex_unlock(&lkb->lkb_cb_mutex);
    @@ -288,7 +288,9 @@ void dlm_callback_stop(struct dlm_ls *ls

    void dlm_callback_suspend(struct dlm_ls *ls)
    {
    + mutex_lock(&ls->ls_cb_mutex);
    set_bit(LSFL_CB_DELAY, &ls->ls_flags);
    + mutex_unlock(&ls->ls_cb_mutex);

    if (ls->ls_callback_wq)
    flush_workqueue(ls->ls_callback_wq);

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