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    Subject[PATCH 3.13 087/160] serial: 8250: Fix thread unsafe __dma_tx_complete function
    Date
    3.13.11.3 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Loic Poulain <loic.poulain@intel.com>

    commit f8fd1b0350d3a4581125f5eda6528f5a2c5f9183 upstream.

    __dma_tx_complete is not protected against concurrent
    call of serial8250_tx_dma. it can lead to circular tail
    index corruption or parallel call of serial_tx_dma on the
    same data portion.

    This patch fixes this issue by holding the port lock.

    Signed-off-by: Loic Poulain <loic.poulain@intel.com>
    Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    drivers/tty/serial/8250/8250_dma.c | 9 +++++++--
    1 file changed, 7 insertions(+), 2 deletions(-)

    diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
    index 7046769..ab9096d 100644
    --- a/drivers/tty/serial/8250/8250_dma.c
    +++ b/drivers/tty/serial/8250/8250_dma.c
    @@ -20,12 +20,15 @@ static void __dma_tx_complete(void *param)
    struct uart_8250_port *p = param;
    struct uart_8250_dma *dma = p->dma;
    struct circ_buf *xmit = &p->port.state->xmit;
    -
    - dma->tx_running = 0;
    + unsigned long flags;

    dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
    UART_XMIT_SIZE, DMA_TO_DEVICE);

    + spin_lock_irqsave(&p->port.lock, flags);
    +
    + dma->tx_running = 0;
    +
    xmit->tail += dma->tx_size;
    xmit->tail &= UART_XMIT_SIZE - 1;
    p->port.icount.tx += dma->tx_size;
    @@ -35,6 +38,8 @@ static void __dma_tx_complete(void *param)

    if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port))
    serial8250_tx_dma(p);
    +
    + spin_unlock_irqrestore(&p->port.lock, flags);
    }

    static void __dma_rx_complete(void *param)
    --
    1.9.1


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