linux-kernel - [PATCH 1/2] parport: fix attempt to write duplicate procfiles

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Date:   Mon,  6 Mar 2017 23:23:42 +0000
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>
Cc:     linux-kernel@...r.kernel.org, James Feeney <james@...ealm.net>,
        Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>,
        stable <stable@...r.kernel.org>
Subject: [PATCH 1/2] parport: fix attempt to write duplicate procfiles

Usually every parallel port will have a single pardev registered with
it. But ppdev driver is an exception. This userspace parallel port
driver allows to create multiple parrallel port devices for a single
parallel port. And as a result we were having a nice warning like:
"sysctl table check failed:
/dev/parport/parport0/devices/ppdev0/timeslice Sysctl already exists"

Use the same logic as used in parport_register_device() and register
the proc files only once for each parallel port.

Fixes: 6fa45a226897 ("parport: add device-model to parport subsystem")
Cc: stable <stable@...r.kernel.org> # v4.4+
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1414656
Bugzilla: https://bugs.archlinux.org/task/52322
Tested-by: James Feeney <james@...ealm.net>
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>
---
 drivers/parport/share.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/parport/share.c b/drivers/parport/share.c
index bc090da..5dc53d4 100644
--- a/drivers/parport/share.c
+++ b/drivers/parport/share.c
@@ -939,8 +939,10 @@ parport_register_dev_model(struct parport *port, const char *name,
 	 * pardevice fields. -arca
 	 */
 	port->ops->init_state(par_dev, par_dev->state);
-	port->proc_device = par_dev;
-	parport_device_proc_register(par_dev);
+	if (!test_and_set_bit(PARPORT_DEVPROC_REGISTERED, &port->devflags)) {
+		port->proc_device = par_dev;
+		parport_device_proc_register(par_dev);
+	}
 
 	return par_dev;
 
-- 
2.1.4