linux-kernel - [PATCH 4.4 121/131] Disable kgdboc failed by echo space to /sys/module/kgdboc/parameters/kgdboc

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Message-Id: <20190401170101.655272460@linuxfoundation.org>
Date:   Mon,  1 Apr 2019 19:03:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Wentao Wang <witallwang@...il.com>,
        Daniel Thompson <daniel.thompson@...aro.org>
Subject: [PATCH 4.4 121/131] Disable kgdboc failed by echo space to /sys/module/kgdboc/parameters/kgdboc

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Wentao Wang <witallwang@...il.com>

commit 3ec8002951ea173e24b466df1ea98c56b7920e63 upstream.

Echo "" to /sys/module/kgdboc/parameters/kgdboc will fail with "No such
device” error.

This is caused by function "configure_kgdboc" who init err to ENODEV
when the config is empty (legal input) the code go out with ENODEV
returned.

Fixes: 2dd453168643 ("kgdboc: Fix restrict error")
Signed-off-by: Wentao Wang <witallwang@...il.com>
Cc: stable <stable@...r.kernel.org>
Acked-by: Daniel Thompson <daniel.thompson@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/tty/serial/kgdboc.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -148,8 +148,10 @@ static int configure_kgdboc(void)
 	char *cptr = config;
 	struct console *cons;
 
-	if (!strlen(config) || isspace(config[0]))
+	if (!strlen(config) || isspace(config[0])) {
+		err = 0;
 		goto noconfig;
+	}
 
 	kgdboc_io_ops.is_console = 0;
 	kgdb_tty_driver = NULL;