serial: 8250_dma: Fix DMA Rx completion race

stable inclusion
from stable-v4.19.273
commit 86bd9f9d11a24bfd072f38c43f4b2664c54a2c2c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6KOHU
CVE: NA

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

commit 31352811 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: NGilles BULOZ <gilles.buloz@kontron.com>
Tested-by: NGilles BULOZ <gilles.buloz@kontron.com>
Fixes: 9ee4b83e ("serial: 8250: Add support for dmaengine")
Cc: stable@vger.kernel.org
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230130114841.25749-2-ilpo.jarvinen@linux.intel.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

drivers/tty/serial/8250/8250_dma.c

@@ -61,6 +61,18 @@ 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;
@@ -126,7 +138,7 @@ 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);