The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Possible dependencies:

31352811e13d ("serial: 8250_dma: Fix DMA Rx completion race") 56dc5074cbec ("serial: 8250_dma: Rearm DMA Rx if more data is pending")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 31352811e13dc2313f101b890fd4b1ce760b5fe7 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= ilpo.jarvinen@linux.intel.com Date: Mon, 30 Jan 2023 13:48:40 +0200 Subject: [PATCH] serial: 8250_dma: Fix DMA Rx completion race MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

__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: 9ee4b83e51f7 ("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.c... 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 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);