[PATCH 21/24] serial: samsung: don't leak the tty on an RX IRQ

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Josef Bacik <josef@toxicpanda.com>

s3c24xx_serial_rx_chars_dma() starts by taking a reference to the tty.
If the interrupt is not a receive timeout, it switches the port from PIO
back to DMA and leaves through the "finish" label, which does not drop
the reference.

A port with RX DMA changes to PIO on every receive timeout, that is at
the end of every burst of data, and comes back this way when the next
burst starts.  So each burst takes a reference which is never dropped,
and the tty structure is not freed when the port is closed for the last
time.

Drop the reference on both paths.

Fixes: b543c301c2c5 ("serial: samsung: add DMA support for RX")
Cc: stable <stable@kernel.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Peter Griffin <peter.griffin@linaro.org>
Cc: Alim Akhtar <alim.akhtar@samsung.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/samsung_tty.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index 640f85e2d636..c9a870a8d155 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -736,14 +736,13 @@ static irqreturn_t s3c24xx_serial_rx_chars_dma(struct s3c24xx_uart_port *ourport
 
 	s3c24xx_serial_rx_drain_fifo(ourport);
 
-	if (tty) {
+	if (tty)
 		tty_flip_buffer_push(t);
-		tty_kref_put(tty);
-	}
 
 	wr_regl(port, S3C2410_UTRSTAT, S3C2410_UTRSTAT_TIMEOUT);
 
 finish:
+	tty_kref_put(tty);
 	uart_port_unlock(port);
 
 	return IRQ_HANDLED;

-- 
2.56.0