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From: Krzysztof Kozlowski <>
To: Greg Kroah-Hartman <>,
	Jiri Slaby <>,,
Cc: Kevin Hilman <>,
	Javier Martinez Canillas <>,, Krzysztof Kozlowski <>,
	Bartlomiej Zolnierkiewicz <>,
Subject: [RESEND PATCH v2 1/2] serial: samsung: Fix ERR pointer dereference on deferred probe
Date: Thu, 16 Jun 2016 08:27:35 +0200	[thread overview]
Message-ID: <> (raw)

When the clk_get() of "uart" clock returns EPROBE_DEFER, the next re-probe
finishes with success but uses invalid (ERR_PTR) values.  This leads to
dereferencing of ERR_PTR stored under ourport->clk:

	12c30000.serial: Controller clock not found
	12c30000.serial: ttySAC3 at MMIO 0x12c30000 (irq = 61, base_baud = 0) is a S3C6400/10
	Unable to handle kernel paging request at virtual address fffffdfb

	(clk_prepare) from [<c039f7d0>] (s3c24xx_serial_pm+0x20/0x128)
	(s3c24xx_serial_pm) from [<c0395414>] (uart_change_pm+0x38/0x40)
	(uart_change_pm) from [<c039689c>] (uart_add_one_port+0x31c/0x44c)
	(uart_add_one_port) from [<c03a035c>] (s3c24xx_serial_probe+0x2a8/0x418)
	(s3c24xx_serial_probe) from [<c03ee110>] (platform_drv_probe+0x50/0xb0)
	(platform_drv_probe) from [<c03ecb44>] (driver_probe_device+0x1f4/0x2b0)
	(driver_probe_device) from [<c03eb0c0>] (bus_for_each_drv+0x44/0x8c)
	(bus_for_each_drv) from [<c03ec8c8>] (__device_attach+0x9c/0x100)
	(__device_attach) from [<c03ebf54>] (bus_probe_device+0x84/0x8c)
	(bus_probe_device) from [<c03ec388>] (deferred_probe_work_func+0x60/0x8c)
	(deferred_probe_work_func) from [<c012fee4>] (process_one_work+0x120/0x328)
	(process_one_work) from [<c0130150>] (worker_thread+0x2c/0x4ac)
	(worker_thread) from [<c0135320>] (kthread+0xd8/0xf4)
	(kthread) from [<c0107978>] (ret_from_fork+0x14/0x3c)

The first unsuccessful clk_get() causes s3c24xx_serial_init_port() to
exit with failure but the s3c24xx_uart_port is left half-configured
(e.g. port->mapbase is set, clk contains ERR_PTR).  On next re-probe,
the function s3c24xx_serial_init_port() will exit early with success
because of configured port->mapbase and driver will use old values,
including the ERR_PTR as clock.

Fix this by cleaning the port->mapbase on error path so each re-probe
will initialize all of the port settings.

Fixes: 60e93575476f ("serial: samsung: enable clock before clearing pending interrupts during init")
Cc: <>
Signed-off-by: Krzysztof Kozlowski <>
Reviewed-by: Javier Martinez Canillas <>
Tested-by: Javier Martinez Canillas <>
Tested-by: Kevin Hilman <>

Changes since v1:
1. Apply suggestion from Bartlomiej (offline) that early check for
   port->mapbase in s3c24xx_serial_init_port() should fail if it is
   already set.  The port->mapbase is now always cleared when probe
   fails, so re-probing with 'port->mapbase != 0' is unexpected.
 drivers/tty/serial/samsung.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index 99bb23161dd6..f0bd2ec0db59 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1684,7 +1684,7 @@ static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
 		return -ENODEV;
 	if (port->mapbase != 0)
-		return 0;
+		return -EINVAL;
 	/* setup info for port */
 	port->dev	= &platdev->dev;
@@ -1738,22 +1738,25 @@ static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
 		ourport->dma = devm_kzalloc(port->dev,
-		if (!ourport->dma)
-			return -ENOMEM;
+		if (!ourport->dma) {
+			ret = -ENOMEM;
+			goto err;
+		}
 	ourport->clk	= clk_get(&platdev->dev, "uart");
 	if (IS_ERR(ourport->clk)) {
 		pr_err("%s: Controller clock not found\n",
-		return PTR_ERR(ourport->clk);
+		ret = PTR_ERR(ourport->clk);
+		goto err;
 	ret = clk_prepare_enable(ourport->clk);
 	if (ret) {
 		pr_err("uart: clock failed to prepare+enable: %d\n", ret);
-		return ret;
+		goto err;
 	/* Keep all interrupts masked and cleared */
@@ -1769,7 +1772,12 @@ static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
 	/* reset the fifos (and setup the uart) */
 	s3c24xx_serial_resetport(port, cfg);
 	return 0;
+	port->mapbase = 0;
+	return ret;
 /* Device driver serial port probe */

             reply	other threads:[~2016-06-16  6:27 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-16  6:27 Krzysztof Kozlowski [this message]
2016-06-16  6:27 ` [RESEND PATCH v2 2/2] serial: samsung: Fix possible out of bounds access on non-DT platform Krzysztof Kozlowski

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