From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Genoud Subject: [PATCH] tty/serial: atmel: fix race condition (TX+DMA) Date: Mon, 20 Mar 2017 11:52:41 +0100 Message-ID: <20170320105241.25648-1-richard.genoud@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Greg Kroah-Hartman Cc: Richard Genoud , "stable # 3 . 12+" , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-serial@vger.kernel.org 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 Signed-off-by: Richard Genoud Cc: stable # 3.12+ --- NB: this will apply on kernels 4.3+, for kernels before 4.3, the code will be: sg_dma_len(&atmel_port->sg_tx) = 0; 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 d9c05e05d896..5c23fb4e552b 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -1954,6 +1954,11 @@ static void atmel_flush_buffer(struct uart_port *port) 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; } /*