driver core: Fix device link device name collision

The device link device's name was of the form:
<supplier-dev-name>--<consumer-dev-name>

This can cause name collision as reported here [1] as device names are
not globally unique. Since device names have to be unique within the
bus/class, add the bus/class name as a prefix to the device names used to
construct the device link device name.

So the devuce link device's name will be of the form:
<supplier-bus-name>:<supplier-dev-name>--<consumer-bus-name>:<consumer-dev-name>

[1] - https://lore.kernel.org/lkml/20201229033440.32142-1-michael@walle.cc/

Fixes: 287905e68dd2 ("driver core: Expose device link details in sysfs")
Cc: stable@vger.kernel.org
Reported-by: Michael Walle <michael@walle.cc>
Tested-by: Michael Walle <michael@walle.cc>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20210110175408.1465657-1-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 15 insertions, 12 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 3819fd012e27..78f6db169d47 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -471,7 +471,9 @@ static int devlink_add_symlinks(struct device *dev,
 	struct device *con = link->consumer;
 	char *buf;
 
-	len = max(strlen(dev_name(sup)), strlen(dev_name(con)));
+	len = max(strlen(dev_bus_name(sup)) + strlen(dev_name(sup)),
+		  strlen(dev_bus_name(con)) + strlen(dev_name(con)));
+	len += strlen(":");
 	len += strlen("supplier:") + 1;
 	buf = kzalloc(len, GFP_KERNEL);
 	if (!buf)
@@ -485,12 +487,12 @@ static int devlink_add_symlinks(struct device *dev,
 	if (ret)
 		goto err_con;
 
-	snprintf(buf, len, "consumer:%s", dev_name(con));
+	snprintf(buf, len, "consumer:%s:%s", dev_bus_name(con), dev_name(con));
 	ret = sysfs_create_link(&sup->kobj, &link->link_dev.kobj, buf);
 	if (ret)
 		goto err_con_dev;
 
-	snprintf(buf, len, "supplier:%s", dev_name(sup));
+	snprintf(buf, len, "supplier:%s:%s", dev_bus_name(sup), dev_name(sup));
 	ret = sysfs_create_link(&con->kobj, &link->link_dev.kobj, buf);
 	if (ret)
 		goto err_sup_dev;
@@ -498,7 +500,7 @@ static int devlink_add_symlinks(struct device *dev,
 	goto out;
 
 err_sup_dev:
-	snprintf(buf, len, "consumer:%s", dev_name(con));
+	snprintf(buf, len, "consumer:%s:%s", dev_bus_name(con), dev_name(con));
 	sysfs_remove_link(&sup->kobj, buf);
 err_con_dev:
 	sysfs_remove_link(&link->link_dev.kobj, "consumer");
@@ -521,7 +523,9 @@ static void devlink_remove_symlinks(struct device *dev,
 	sysfs_remove_link(&link->link_dev.kobj, "consumer");
 	sysfs_remove_link(&link->link_dev.kobj, "supplier");
 
-	len = max(strlen(dev_name(sup)), strlen(dev_name(con)));
+	len = max(strlen(dev_bus_name(sup)) + strlen(dev_name(sup)),
+		  strlen(dev_bus_name(con)) + strlen(dev_name(con)));
+	len += strlen(":");
 	len += strlen("supplier:") + 1;
 	buf = kzalloc(len, GFP_KERNEL);
 	if (!buf) {
@@ -529,9 +533,9 @@ static void devlink_remove_symlinks(struct device *dev,
 		return;
 	}
 
-	snprintf(buf, len, "supplier:%s", dev_name(sup));
+	snprintf(buf, len, "supplier:%s:%s", dev_bus_name(sup), dev_name(sup));
 	sysfs_remove_link(&con->kobj, buf);
-	snprintf(buf, len, "consumer:%s", dev_name(con));
+	snprintf(buf, len, "consumer:%s:%s", dev_bus_name(con), dev_name(con));
 	sysfs_remove_link(&sup->kobj, buf);
 	kfree(buf);
 }
@@ -752,8 +756,9 @@ struct device_link *device_link_add(struct device *consumer,
 
 	link->link_dev.class = &devlink_class;
 	device_set_pm_not_required(&link->link_dev);
-	dev_set_name(&link->link_dev, "%s--%s",
-		     dev_name(supplier), dev_name(consumer));
+	dev_set_name(&link->link_dev, "%s:%s--%s:%s",
+		     dev_bus_name(supplier), dev_name(supplier),
+		     dev_bus_name(consumer), dev_name(consumer));
 	if (device_register(&link->link_dev)) {
 		put_device(consumer);
 		put_device(supplier);
@@ -1823,9 +1828,7 @@ const char *dev_driver_string(const struct device *dev)
 	 * never change once they are set, so they don't need special care.
 	 */
 	drv = READ_ONCE(dev->driver);
-	return drv ? drv->name :
-			(dev->bus ? dev->bus->name :
-			(dev->class ? dev->class->name : ""));
+	return drv ? drv->name : dev_bus_name(dev);
 }
 EXPORT_SYMBOL(dev_driver_string);