4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Richard Genoud <richard.genoud@xxxxxxxxx> 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@xxxxxxxxxxxxx> Signed-off-by: Richard Genoud <richard.genoud@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -1987,6 +1987,11 @@ static void atmel_flush_buffer(struct ua atmel_uart_writel(port, ATMEL_PDC_TCR, 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; } /*