[PATCH 4.9 002/152] ppdev: fix registering same device name

[Greg Kroah-Hartman]

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

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

From: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>

commit 9a69645dde1188723d80745c1bc6ee9af2cbe2a7 upstream.

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 big warning like:
"sysfs: cannot create duplicate filename '/devices/parport0/ppdev0.0'".
And with that many parallel port printers stopped working.

We have been using the minor number as the id field while registering
a parralel port device with a parralel port. But when there are
multiple parrallel port device for one single parallel port, they all
tried to register with the same name like 'pardev0.0' and everything
started failing.
Use an incremented index as the id instead of the minor number.

Fixes: 8b7d3a9d903e ("ppdev: use new parport device model")
Cc: stable <stable@xxxxxxxxxxxxxxx> # v4.9+
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1414656
Bugzilla: https://bugs.archlinux.org/task/52322
Tested-by: James Feeney <james@xxxxxxxxxxx>
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>


---
 drivers/char/ppdev.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/drivers/char/ppdev.c
+++ b/drivers/char/ppdev.c
@@ -84,11 +84,14 @@ struct pp_struct {
 	struct ieee1284_info state;
 	struct ieee1284_info saved_state;
 	long default_inactivity;
+	int index;
 };
 
 /* should we use PARDEVICE_MAX here? */
 static struct device *devices[PARPORT_MAX];
 
+static DEFINE_IDA(ida_index);
+
 /* pp_struct.flags bitfields */
 #define PP_CLAIMED    (1<<0)
 #define PP_EXCL       (1<<1)
@@ -290,6 +293,7 @@ static int register_device(int minor, st
 	struct pardevice *pdev = NULL;
 	char *name;
 	struct pardev_cb ppdev_cb;
+	int index;
 
 	name = kasprintf(GFP_KERNEL, CHRDEV "%x", minor);
 	if (name == NULL)
@@ -302,20 +306,23 @@ static int register_device(int minor, st
 		return -ENXIO;
 	}
 
+	index = ida_simple_get(&ida_index, 0, 0, GFP_KERNEL);
 	memset(&ppdev_cb, 0, sizeof(ppdev_cb));
 	ppdev_cb.irq_func = pp_irq;
 	ppdev_cb.flags = (pp->flags & PP_EXCL) ? PARPORT_FLAG_EXCL : 0;
 	ppdev_cb.private = pp;
-	pdev = parport_register_dev_model(port, name, &ppdev_cb, minor);
+	pdev = parport_register_dev_model(port, name, &ppdev_cb, index);
 	parport_put_port(port);
 
 	if (!pdev) {
 		printk(KERN_WARNING "%s: failed to register device!\n", name);
+		ida_simple_remove(&ida_index, index);
 		kfree(name);
 		return -ENXIO;
 	}
 
 	pp->pdev = pdev;
+	pp->index = index;
 	dev_dbg(&pdev->dev, "registered pardevice\n");
 	return 0;
 }
@@ -752,6 +759,7 @@ static int pp_release(struct inode *inod
 
 	if (pp->pdev) {
 		parport_unregister_device(pp->pdev);
+		ida_simple_remove(&ida_index, pp->index);
 		pp->pdev = NULL;
 		pr_debug(CHRDEV "%x: unregistered pardevice\n", minor);
 	}