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Subject[PATCH 4.14 017/166] serial: 8250: Avoid error message on reprobe
From: Lukas Wunner <>

commit e0a851fe6b9b619527bd928aa93caaddd003f70c upstream.

If the call to uart_add_one_port() in serial8250_register_8250_port()
fails, a half-initialized entry in the serial_8250ports[] array is left

A subsequent reprobe of the same serial port causes that entry to be
reused. Because uart-> is set, uart_remove_one_port() is called
for the half-initialized entry and bails out with an error message:

bcm2835-aux-uart 3f215040.serial: Removing wrong port: (null) != (ptrval)

The same happens on failure of mctrl_gpio_init() since commit
4a96895f74c9 ("tty/serial/8250: use mctrl_gpio helpers").

Fix by zeroing the uart-> pointer in the probe error path.

The bug was introduced in v2.6.10 by historical commit befff6f5bf5f
("[SERIAL] Add new port registration/unregistration functions."):

The commit added an unconditional call to uart_remove_one_port() in
serial8250_register_port(). In v3.7, commit 835d844d1a28 ("8250_pnp:
do pnp probe before legacy probe") made that call conditional on
uart-> which allows me to fix the issue by zeroing that pointer
in the error path. Thus, the present commit will fix the problem as far
back as v3.7 whereas still older versions need to also cherry-pick

Fixes: 835d844d1a28 ("8250_pnp: do pnp probe before legacy probe")
Signed-off-by: Lukas Wunner <>
Cc: # v2.6.10
Cc: # v2.6.10: 835d844d1a28: 8250_pnp: do pnp probe before legacy
Reviewed-by: Andy Shevchenko <>
[iwamatsu: Backported to 4.14, 4.19: adjust context]
Signed-off-by: Nobuhiro Iwamatsu (CIP) <>
Signed-off-by: Greg Kroah-Hartman <>
drivers/tty/serial/8250/8250_core.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1065,8 +1065,10 @@ int serial8250_register_8250_port(struct
ret = uart_add_one_port(&serial8250_reg,
- if (ret == 0)
- ret = uart->port.line;
+ if (ret)
+ goto err;
+ ret = uart->port.line;
} else {
"skipping CIR port at 0x%lx / 0x%llx, IRQ %d\n",
@@ -1091,6 +1093,11 @@ int serial8250_register_8250_port(struct

return ret;
+ uart-> = NULL;
+ mutex_unlock(&serial_mutex);
+ return ret;

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