On Mon, Jan 30, 2023 at 01:48:40PM +0200, Ilpo Järvinen wrote:
> __dma_rx_complete() is called from two places:
> - Through the DMA completion callback dma_rx_complete()
> - From serial8250_rx_dma_flush() after IIR_RLSI or IIR_RX_TIMEOUT
> The former does not hold port's lock during __dma_rx_complete() which
> allows these two to race and potentially insert the same data twice.
>
> Extend port's lock coverage in dma_rx_complete() to prevent the race
> and check if the DMA Rx is still pending completion before calling
> into __dma_rx_complete().
>
> Reported-by: Gilles BULOZ <gilles.buloz@xxxxxxxxxxx>
> Tested-by: Gilles BULOZ <gilles.buloz@xxxxxxxxxxx>
> Fixes: 9ee4b83e51f7 ("serial: 8250: Add support for dmaengine")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
FWIW:
Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> 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 37d6af2ec427..5594883a96f8 100644
> --- a/drivers/tty/serial/8250/8250_dma.c
> +++ b/drivers/tty/serial/8250/8250_dma.c
> @@ -62,9 +62,14 @@ static void dma_rx_complete(void *param)
> struct uart_8250_dma *dma = p->dma;
> unsigned long flags;
>
> - __dma_rx_complete(p);
> -
> spin_lock_irqsave(&p->port.lock, flags);
> + if (dma->rx_running)
> + __dma_rx_complete(p);
> +
> + /*
> + * Cannot be combined with the previous check because __dma_rx_complete()
> + * changes dma->rx_running.
> + */
> if (!dma->rx_running && (serial_lsr_in(p) & UART_LSR_DR))
> p->dma->rx_dma(p);
> spin_unlock_irqrestore(&p->port.lock, flags);
> --
> 2.30.2
--
heikki
