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    Subject[PATCH 5.15 226/846] mwifiex: Fix possible ABBA deadlock
    Date
    From: Brian Norris <briannorris@chromium.org>

    [ Upstream commit 1b8bb8919ef81bfc8873d223b9361f1685f2106d ]

    Quoting Jia-Ju Bai <baijiaju1990@gmail.com>:

    mwifiex_dequeue_tx_packet()
    spin_lock_bh(&priv->wmm.ra_list_spinlock); --> Line 1432 (Lock A)
    mwifiex_send_addba()
    spin_lock_bh(&priv->sta_list_spinlock); --> Line 608 (Lock B)

    mwifiex_process_sta_tx_pause()
    spin_lock_bh(&priv->sta_list_spinlock); --> Line 398 (Lock B)
    mwifiex_update_ralist_tx_pause()
    spin_lock_bh(&priv->wmm.ra_list_spinlock); --> Line 941 (Lock A)

    Similar report for mwifiex_process_uap_tx_pause().

    While the locking expectations in this driver are a bit unclear, the
    Fixed commit only intended to protect the sta_ptr, so we can drop the
    lock as soon as we're done with it.

    IIUC, this deadlock cannot actually happen, because command event
    processing (which calls mwifiex_process_sta_tx_pause()) is
    sequentialized with TX packet processing (e.g.,
    mwifiex_dequeue_tx_packet()) via the main loop (mwifiex_main_process()).
    But it's good not to leave this potential issue lurking.

    Fixes: f0f7c2275fb9 ("mwifiex: minor cleanups w/ sta_list_spinlock in cfg80211.c")
    Cc: Douglas Anderson <dianders@chromium.org>
    Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
    Link: https://lore.kernel.org/linux-wireless/0e495b14-efbb-e0da-37bd-af6bd677ee2c@gmail.com/
    Signed-off-by: Brian Norris <briannorris@chromium.org>
    Reviewed-by: Douglas Anderson <dianders@chromium.org>
    Signed-off-by: Kalle Valo <kvalo@kernel.org>
    Link: https://lore.kernel.org/r/YaV0pllJ5p/EuUat@google.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/wireless/marvell/mwifiex/sta_event.c | 8 ++++++--
    1 file changed, 6 insertions(+), 2 deletions(-)

    diff --git a/drivers/net/wireless/marvell/mwifiex/sta_event.c b/drivers/net/wireless/marvell/mwifiex/sta_event.c
    index 68c63268e2e6b..2b2e6e0166e14 100644
    --- a/drivers/net/wireless/marvell/mwifiex/sta_event.c
    +++ b/drivers/net/wireless/marvell/mwifiex/sta_event.c
    @@ -365,10 +365,12 @@ static void mwifiex_process_uap_tx_pause(struct mwifiex_private *priv,
    sta_ptr = mwifiex_get_sta_entry(priv, tp->peermac);
    if (sta_ptr && sta_ptr->tx_pause != tp->tx_pause) {
    sta_ptr->tx_pause = tp->tx_pause;
    + spin_unlock_bh(&priv->sta_list_spinlock);
    mwifiex_update_ralist_tx_pause(priv, tp->peermac,
    tp->tx_pause);
    + } else {
    + spin_unlock_bh(&priv->sta_list_spinlock);
    }
    - spin_unlock_bh(&priv->sta_list_spinlock);
    }
    }

    @@ -400,11 +402,13 @@ static void mwifiex_process_sta_tx_pause(struct mwifiex_private *priv,
    sta_ptr = mwifiex_get_sta_entry(priv, tp->peermac);
    if (sta_ptr && sta_ptr->tx_pause != tp->tx_pause) {
    sta_ptr->tx_pause = tp->tx_pause;
    + spin_unlock_bh(&priv->sta_list_spinlock);
    mwifiex_update_ralist_tx_pause(priv,
    tp->peermac,
    tp->tx_pause);
    + } else {
    + spin_unlock_bh(&priv->sta_list_spinlock);
    }
    - spin_unlock_bh(&priv->sta_list_spinlock);
    }
    }
    }
    --
    2.34.1


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