diff mbox series

[for,4.4,4.9] serial: 8250: Avoid error message on reprobe

Message ID 20200925093043.388596-1-nobuhiro1.iwamatsu@toshiba.co.jp
State New
Headers show
Series [for,4.4,4.9] serial: 8250: Avoid error message on reprobe | expand

Commit Message

Nobuhiro Iwamatsu Sept. 25, 2020, 9:30 a.m. UTC 
From: Lukas Wunner <lukas@wunner.de>

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
behind.

A subsequent reprobe of the same serial port causes that entry to be
reused.  Because uart->port.dev 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->port.dev 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."):
https://git.kernel.org/tglx/history/c/befff6f5bf5f

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->port.dev 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
835d844d1a28.

Fixes: 835d844d1a28 ("8250_pnp: do pnp probe before legacy probe")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org # v2.6.10
Cc: stable@vger.kernel.org # v2.6.10: 835d844d1a28: 8250_pnp: do pnp probe before legacy
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/b4a072013ee1a1d13ee06b4325afb19bda57ca1b.1589285873.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[iwamatsu: Backported to 4.4, 4.9: adjust context]
Signed-off-by: Nobuhiro Iwamatsu (CIP) <nobuhiro1.iwamatsu@toshiba.co.jp>
---
 drivers/tty/serial/8250/8250_core.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index e9ea9005a984..f24fa99da69f 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1037,8 +1037,10 @@  int serial8250_register_8250_port(struct uart_8250_port *up)
 
 			ret = uart_add_one_port(&serial8250_reg,
 						&uart->port);
-			if (ret == 0)
-				ret = uart->port.line;
+			if (ret)
+				goto err;
+
+			ret = uart->port.line;
 		} else {
 			dev_info(uart->port.dev,
 				"skipping CIR port at 0x%lx / 0x%llx, IRQ %d\n",
@@ -1052,6 +1054,11 @@  int serial8250_register_8250_port(struct uart_8250_port *up)
 	mutex_unlock(&serial_mutex);
 
 	return ret;
+
+err:
+	uart->port.dev = NULL;
+	mutex_unlock(&serial_mutex);
+	return ret;
 }
 EXPORT_SYMBOL(serial8250_register_8250_port);