patch "tty/serial: atmel: fix race condition (TX+DMA)" added to tty-linus

This is a note to let you know that I've just added the patch titled

tty/serial: atmel: fix race condition (TX+DMA)

to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From: Richard Genoud <[email protected]>
Date: Mon, 20 Mar 2017 11:52:41 +0100
Subject: tty/serial: atmel: fix race condition (TX+DMA)

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).

---
 drivers/tty/serial/atmel_serial.c | 5 +++++
 1 file changed, 5 insertions(+)

index dcebb28ffbc4..5f644515ed33 100644
@@ -1951,6 +1951,11 @@ 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;
 }
 
 /*

2.12.1