linux-kernel - [PATCH][serial-next][V2] serial-uartlite: fix null pointer dereference on pointer port

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Date:   Tue, 13 Nov 2018 09:43:23 +0000
From:   Colin King <colin.king@...onical.com>
To:     Peter Korsgaard <jacmet@...site.dk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][serial-next][V2] serial-uartlite: fix null pointer dereference on pointer port

From: Colin Ian King <colin.king@...onical.com>

Pointer port is dereferenced on port->private_data when assigning pointer
pdata before port is null checked, leading to a potential null pointer
dereference.  Fix this by assigning pdata after the null pointer check on
port.

Detected by CoverityScan, CID#1475434 ("Dereference before null check")

Fixes: 3b209d253e7f ("serial-uartlite: Do not use static struct uart_driver out of probe()")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/tty/serial/uartlite.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/uartlite.c b/drivers/tty/serial/uartlite.c
index 4a7989df5ff5..b8b912b5a8b9 100644
--- a/drivers/tty/serial/uartlite.c
+++ b/drivers/tty/serial/uartlite.c
@@ -694,10 +694,11 @@ static int ulite_assign(struct device *dev, int id, u32 base, int irq,
 static int ulite_release(struct device *dev)
 {
 	struct uart_port *port = dev_get_drvdata(dev);
-	struct uartlite_data *pdata = port->private_data;
 	int rc = 0;
 
 	if (port) {
+		struct uartlite_data *pdata = port->private_data;
+
 		rc = uart_remove_one_port(pdata->ulite_uart_driver, port);
 		dev_set_drvdata(dev, NULL);
 		port->mapbase = 0;
@@ -715,10 +716,12 @@ static int ulite_release(struct device *dev)
 static int __maybe_unused ulite_suspend(struct device *dev)
 {
 	struct uart_port *port = dev_get_drvdata(dev);
-	struct uartlite_data *pdata = port->private_data;
 
-	if (port)
+	if (port) {
+		struct uartlite_data *pdata = port->private_data;
+
 		uart_suspend_port(pdata->ulite_uart_driver, port);
+	}
 
 	return 0;
 }
@@ -732,10 +735,12 @@ static int __maybe_unused ulite_suspend(struct device *dev)
 static int __maybe_unused ulite_resume(struct device *dev)
 {
 	struct uart_port *port = dev_get_drvdata(dev);
-	struct uartlite_data *pdata = port->private_data;
 
-	if (port)
+	if (port) {
+		struct uartlite_data *pdata = port->private_data;
+
 		uart_resume_port(pdata->ulite_uart_driver, port);
+	}
 
 	return 0;
 }
-- 
2.19.1