serial: 8250_dma: Fix DMA Rx completion race

commit 31352811e13dc2313f101b890fd4b1ce760b5fe7 upstream.

__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@kontron.com>
Tested-by: Gilles BULOZ <gilles.buloz@kontron.com>
Fixes: 1cfdaf055998 ("serial: 8250: Add support for dmaengine")
Cc: stable@vger.kernel.org
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230130114841.25749-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index b85c82616e8cbb8d7853dfd5c0fef202299803b8..cc521f6232fdcb4befcba9158a0d6c268827ee02 100644 (file)
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -57,6 +57,18 @@ static void __dma_rx_complete(void *param)
        tty_flip_buffer_push(tty_port);
 }
 
+static void dma_rx_complete(void *param)
+{
+       struct uart_8250_port *p = param;
+       struct uart_8250_dma *dma = p->dma;
+       unsigned long flags;
+
+       spin_lock_irqsave(&p->port.lock, flags);
+       if (dma->rx_running)
+               __dma_rx_complete(p);
+       spin_unlock_irqrestore(&p->port.lock, flags);
+}
+
 int serial8250_tx_dma(struct uart_8250_port *p)
 {
        struct uart_8250_dma            *dma = p->dma;
@@ -130,7 +142,7 @@ int serial8250_rx_dma(struct uart_8250_port *p)
                return -EBUSY;
 
        dma->rx_running = 1;
-       desc->callback = __dma_rx_complete;
+       desc->callback = dma_rx_complete;
        desc->callback_param = p;
 
        dma->rx_cookie = dmaengine_submit(desc);