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    Subject[PATCH 5.15 570/846] ath9k_htc: fix NULL pointer dereference at ath9k_htc_rxep()
    Date
    From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>

    [ Upstream commit b0ec7e55fce65f125bd1d7f02e2dc4de62abee34 ]

    syzbot is reporting lockdep warning followed by kernel panic at
    ath9k_htc_rxep() [1], for ath9k_htc_rxep() depends on ath9k_rx_init()
    being already completed.

    Since ath9k_htc_rxep() is set by ath9k_htc_connect_svc(WMI_BEACON_SVC)
    from ath9k_init_htc_services(), it is possible that ath9k_htc_rxep() is
    called via timer interrupt before ath9k_rx_init() from ath9k_init_device()
    is called.

    Since we can't call ath9k_init_device() before ath9k_init_htc_services(),
    let's hold ath9k_htc_rxep() no-op until ath9k_rx_init() completes.

    Link: https://syzkaller.appspot.com/bug?extid=4d2d56175b934b9a7bf9 [1]
    Reported-by: syzbot <syzbot+4d2d56175b934b9a7bf9@syzkaller.appspotmail.com>
    Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Tested-by: syzbot <syzbot+4d2d56175b934b9a7bf9@syzkaller.appspotmail.com>
    Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
    Link: https://lore.kernel.org/r/2b88f416-b2cb-7a18-d688-951e6dc3fe92@i-love.sakura.ne.jp
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/wireless/ath/ath9k/htc.h | 1 +
    drivers/net/wireless/ath/ath9k/htc_drv_txrx.c | 8 ++++++++
    2 files changed, 9 insertions(+)

    diff --git a/drivers/net/wireless/ath/ath9k/htc.h b/drivers/net/wireless/ath/ath9k/htc.h
    index 0a1634238e673..4f71e962279af 100644
    --- a/drivers/net/wireless/ath/ath9k/htc.h
    +++ b/drivers/net/wireless/ath/ath9k/htc.h
    @@ -281,6 +281,7 @@ struct ath9k_htc_rxbuf {
    struct ath9k_htc_rx {
    struct list_head rxbuf;
    spinlock_t rxbuflock;
    + bool initialized;
    };

    #define ATH9K_HTC_TX_CLEANUP_INTERVAL 50 /* ms */
    diff --git a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c b/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
    index 8e69e8989f6d3..e7a21eaf3a68d 100644
    --- a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
    +++ b/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
    @@ -1130,6 +1130,10 @@ void ath9k_htc_rxep(void *drv_priv, struct sk_buff *skb,
    struct ath9k_htc_rxbuf *rxbuf = NULL, *tmp_buf = NULL;
    unsigned long flags;

    + /* Check if ath9k_rx_init() completed. */
    + if (!data_race(priv->rx.initialized))
    + goto err;
    +
    spin_lock_irqsave(&priv->rx.rxbuflock, flags);
    list_for_each_entry(tmp_buf, &priv->rx.rxbuf, list) {
    if (!tmp_buf->in_process) {
    @@ -1185,6 +1189,10 @@ int ath9k_rx_init(struct ath9k_htc_priv *priv)
    list_add_tail(&rxbuf->list, &priv->rx.rxbuf);
    }

    + /* Allow ath9k_htc_rxep() to operate. */
    + smp_wmb();
    + priv->rx.initialized = true;
    +
    return 0;

    err:
    --
    2.34.1


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