serial: samsung: Fix ERR pointer dereference on deferred probe

commit e51e4d8a185de90424b03f30181b35f29c46a25a upstream.

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")
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index 8320173af846b396a40319168b5718f6dd5c816a..237ef5573c1819eeefa078bb03aa221615226092 100644 (file)
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1676,7 +1676,7 @@ 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;
@@ -1730,22 +1730,25 @@ static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
                ourport->dma = devm_kzalloc(port->dev,
                                            sizeof(*ourport->dma),
                                            GFP_KERNEL);
-               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",
                                dev_name(&platdev->dev));
-               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);
                clk_put(ourport->clk);
-               return ret;
+               goto err;
        }
 
        /* Keep all interrupts masked and cleared */
@@ -1761,7 +1764,12 @@ 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;
+
+err:
+       port->mapbase = 0;
+       return ret;
 }
 
 /* Device driver serial port probe */