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Subject[PATCH 3.16 022/346] serial: samsung: Fix ERR pointer dereference on deferred probe
3.16.39-rc1 review patch.  If anyone has any objections, please let me know.


From: Krzysztof Kozlowski <>

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 <>
Reviewed-by: Javier Martinez Canillas <>
Tested-by: Javier Martinez Canillas <>
Tested-by: Kevin Hilman <>
Signed-off-by: Greg Kroah-Hartman <>
[bwh: Backported to 3.16: driver doesn't set up DMA here]
Signed-off-by: Ben Hutchings <>
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1163,7 +1163,7 @@ static int s3c24xx_serial_init_port(stru
return -ENODEV;

if (port->mapbase != 0)
- return 0;
+ return -EINVAL;

/* setup info for port */
port->dev = &platdev->dev;
@@ -1213,14 +1213,15 @@ static int s3c24xx_serial_init_port(stru
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 */
@@ -1236,7 +1237,12 @@ static int s3c24xx_serial_init_port(stru

/* reset the fifos (and setup the uart) */
s3c24xx_serial_resetport(port, cfg);
return 0;
+ port->mapbase = 0;
+ return ret;

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