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SubjectRe: [PATCH 3.18 049/124] tty/serial: atmel: fix race condition (TX+DMA)
On Thu, Apr 20, 2017 at 09:46:03AM +0200, Richard Genoud wrote:
> 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;

Thanks for the fix, now updated.

greg k-h

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