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    Subject[PATCH 4.12 006/196] ath9k: fix tx99 use after free
    Date
    4.12-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Miaoqing Pan <miaoqing@codeaurora.org>

    commit cf8ce1ea61b75712a154c93e40f2a5af2e4dd997 upstream.

    One scenario that could lead to UAF is two threads writing
    simultaneously to the "tx99" debug file. One of them would
    set the "start" value to true and follow to ath9k_tx99_init().
    Inside the function it would set the sc->tx99_state to true
    after allocating sc->tx99skb. Then, the other thread would
    execute write_file_tx99() and call ath9k_tx99_deinit().
    sc->tx99_state would be freed. After that, the first thread
    would continue inside ath9k_tx99_init() and call
    r = ath9k_tx99_send(sc, sc->tx99_skb, &txctl);
    that would make use of the freed sc->tx99_skb memory.

    Signed-off-by: Miaoqing Pan <miaoqing@codeaurora.org>
    Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/net/wireless/ath/ath9k/tx99.c | 13 +++++++++----
    1 file changed, 9 insertions(+), 4 deletions(-)

    --- a/drivers/net/wireless/ath/ath9k/tx99.c
    +++ b/drivers/net/wireless/ath/ath9k/tx99.c
    @@ -189,22 +189,27 @@ static ssize_t write_file_tx99(struct fi
    if (strtobool(buf, &start))
    return -EINVAL;

    + mutex_lock(&sc->mutex);
    +
    if (start == sc->tx99_state) {
    if (!start)
    - return count;
    + goto out;
    ath_dbg(common, XMIT, "Resetting TX99\n");
    ath9k_tx99_deinit(sc);
    }

    if (!start) {
    ath9k_tx99_deinit(sc);
    - return count;
    + goto out;
    }

    r = ath9k_tx99_init(sc);
    - if (r)
    + if (r) {
    + mutex_unlock(&sc->mutex);
    return r;
    -
    + }
    +out:
    + mutex_unlock(&sc->mutex);
    return count;
    }


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