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    Subject[PATCH 5.18 229/339] drivers: staging: rtl8192eu: Fix deadlock in rtw_joinbss_event_prehandle
    Date
    From: Duoming Zhou <duoming@zju.edu.cn>

    [ Upstream commit 0fcddf9c7c10202946d5b19409efbdff744fba88 ]

    There is a deadlock in rtw_joinbss_event_prehandle(), which is shown below:

    (Thread 1) | (Thread 2)
    | _set_timer()
    rtw_joinbss_event_prehandle()| mod_timer()
    spin_lock_bh() //(1) | (wait a time)
    ... | rtw_join_timeout_handler()
    | _rtw_join_timeout_handler()
    del_timer_sync() | spin_lock_bh() //(2)
    (wait timer to stop) | ...

    We hold pmlmepriv->lock in position (1) of thread 1 and
    use del_timer_sync() to wait timer to stop, but timer handler
    also need pmlmepriv->lock in position (2) of thread 2.
    As a result, rtw_joinbss_event_prehandle() will block forever.

    This patch extracts del_timer_sync() from the protection of
    spin_lock_bh(), which could let timer handler to obtain
    the needed lock. What`s more, we change spin_lock_bh() to
    spin_lock_irq() in _rtw_join_timeout_handler() in order to
    prevent deadlock.

    Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
    Link: https://lore.kernel.org/r/20220409072135.74248-1-duoming@zju.edu.cn
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/staging/r8188eu/core/rtw_mlme.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    diff --git a/drivers/staging/r8188eu/core/rtw_mlme.c b/drivers/staging/r8188eu/core/rtw_mlme.c
    index 6f0bff186477..76cf6a69bf0f 100644
    --- a/drivers/staging/r8188eu/core/rtw_mlme.c
    +++ b/drivers/staging/r8188eu/core/rtw_mlme.c
    @@ -1071,8 +1071,10 @@ void rtw_joinbss_event_prehandle(struct adapter *adapter, u8 *pbuf)
    rtw_indicate_connect(adapter);
    }

    + spin_unlock_bh(&pmlmepriv->lock);
    /* s5. Cancel assoc_timer */
    del_timer_sync(&pmlmepriv->assoc_timer);
    + spin_lock_bh(&pmlmepriv->lock);
    } else {
    spin_unlock_bh(&pmlmepriv->scanned_queue.lock);
    goto ignore_joinbss_callback;
    @@ -1310,7 +1312,7 @@ void _rtw_join_timeout_handler (struct adapter *adapter)
    if (adapter->bDriverStopped || adapter->bSurpriseRemoved)
    return;

    - spin_lock_bh(&pmlmepriv->lock);
    + spin_lock_irq(&pmlmepriv->lock);

    if (rtw_to_roaming(adapter) > 0) { /* join timeout caused by roaming */
    while (1) {
    @@ -1329,7 +1331,7 @@ void _rtw_join_timeout_handler (struct adapter *adapter)
    rtw_indicate_disconnect(adapter);
    free_scanqueue(pmlmepriv);/* */
    }
    - spin_unlock_bh(&pmlmepriv->lock);
    + spin_unlock_irq(&pmlmepriv->lock);

    }

    --
    2.35.1


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