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SubjectRe: [PATCH 3.18 049/124] tty/serial: atmel: fix race condition (TX+DMA)
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On 20/04/2017 08:35, Greg Kroah-Hartman wrote:
> 3.18-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Richard Genoud <richard.genoud@gmail.com>
>
> commit 31ca2c63fdc0aee725cbd4f207c1256f5deaabde upstream.
>
> If uart_flush_buffer() is called between atmel_tx_dma() and
> atmel_complete_tx_dma(), the circular buffer has been cleared, but not
> atmel_port->tx_len.
> That leads to a circular buffer overflow (dumping (UART_XMIT_SIZE -
> atmel_port->tx_len) bytes).
>
> Tested-by: Nicolas Ferre <nicolas.ferre@microchip.com>
> Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> ---
> drivers/tty/serial/atmel_serial.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -1867,6 +1867,11 @@ static void atmel_flush_buffer(struct ua
> UART_PUT_TCR(port, 0);
> atmel_port->pdc_tx.ofs = 0;
> }
> + /*
> + * in uart_flush_buffer(), the xmit circular buffer has just
> + * been cleared, so we have to reset tx_len accordingly.
> + */
> + atmel_port->tx_len = 0;
> }
>
> /*
>
>
Hi,
This won't compile on 3.18 kernel since ->tx_len doesn't exist yet.

Here is the backported version of this patch:
Thanks !
======================

commit 31ca2c63fdc0aee725cbd4f207c1256f5deaabde upstream.

If uart_flush_buffer() is called between atmel_tx_dma() and
atmel_complete_tx_dma(), the circular buffer has been cleared, but not
its length.
That leads to a circular buffer overflow (dumping (UART_XMIT_SIZE -
sg_dma_len(&atmel_port->sg_tx)) bytes).

Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
---
drivers/tty/serial/atmel_serial.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index daaed7c79e4f..a10c778be2ad 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -1867,6 +1867,11 @@ static void atmel_flush_buffer(struct uart_port *port)
UART_PUT_TCR(port, 0);
atmel_port->pdc_tx.ofs = 0;
}
+ /*
+ * in uart_flush_buffer(), the xmit circular buffer has just
+ * been cleared, so we have to reset its length accordingly.
+ */
+ sg_dma_len(&atmel_port->sg_tx) = 0;
}

/*
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