[PATCH 5.10 143/199] driver core: Fix device link device name collision

Greg Kroah-Hartman
2021-01-26T09:53:40Z

From: Saravana Kannan <saravanak@google.com>

commit e020ff611ba9be54e959e6b548038f8a020da1c9 upstream.

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>

---
Documentation/ABI/testing/sysfs-class-devlink | 4 +--
Documentation/ABI/testing/sysfs-devices-consumer | 5 ++--
Documentation/ABI/testing/sysfs-devices-supplier | 5 ++--
drivers/base/core.c | 27 ++++++++++++-----------
include/linux/device.h | 12 ++++++++++
5 files changed, 35 insertions(+), 18 deletions(-)

--- a/Documentation/ABI/testing/sysfs-class-devlink
+++ b/Documentation/ABI/testing/sysfs-class-devlink
@@ -5,8 +5,8 @@ Description:
Provide a place in sysfs for the device link objects in the
kernel at any given time. The name of a device link directory,
denoted as ... above, is of the form <supplier>--<consumer>
- where <supplier> is the supplier device name and <consumer> is
- the consumer device name.
+ where <supplier> is the supplier bus:device name and <consumer>
+ is the consumer bus:device name.

What: /sys/class/devlink/.../auto_remove_on
Date: May 2020
--- a/Documentation/ABI/testing/sysfs-devices-consumer
+++ b/Documentation/ABI/testing/sysfs-devices-consumer
@@ -4,5 +4,6 @@ Contact: Saravana Kannan <saravanak@goog
Description:
The /sys/devices/.../consumer:<consumer> are symlinks to device
links where this device is the supplier. <consumer> denotes the
- name of the consumer in that device link. There can be zero or
- more of these symlinks for a given device.
+ name of the consumer in that device link and is of the form
+ bus:device name. There can be zero or more of these symlinks
+ for a given device.
--- a/Documentation/ABI/testing/sysfs-devices-supplier
+++ b/Documentation/ABI/testing/sysfs-devices-supplier
@@ -4,5 +4,6 @@ Contact: Saravana Kannan <saravanak@goog
Description:
The /sys/devices/.../supplier:<supplier> are symlinks to device
links where this device is the consumer. <supplier> denotes the
- name of the supplier in that device link. There can be zero or
- more of these symlinks for a given device.
+ name of the supplier in that device link and is of the form
+ bus:device name. There can be zero or more of these symlinks
+ for a given device.
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -363,7 +363,9 @@ static int devlink_add_symlinks(struct d
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)
@@ -377,12 +379,12 @@ static int devlink_add_symlinks(struct d
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;
@@ -390,7 +392,7 @@ static int devlink_add_symlinks(struct d
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");
@@ -413,7 +415,9 @@ static void devlink_remove_symlinks(stru
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) {
@@ -421,9 +425,9 @@ static void devlink_remove_symlinks(stru
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);
}
@@ -633,8 +637,9 @@ struct device_link *device_link_add(stru

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);
@@ -1652,9 +1657,7 @@ const char *dev_driver_string(const stru
* 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);

--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -615,6 +615,18 @@ static inline const char *dev_name(const
return kobject_name(&dev->kobj);
}

+/**
+ * dev_bus_name - Return a device's bus/class name, if at all possible
+ * @dev: struct device to get the bus/class name of
+ *
+ * Will return the name of the bus/class the device is attached to. If it is
+ * not attached to a bus/class, an empty string will be returned.
+ */
+static inline const char *dev_bus_name(const struct device *dev)
+{
+ return dev->bus ? dev->bus->name : (dev->class ? dev->class->name : "");
+}
+
__printf(2, 3) int dev_set_name(struct device *dev, const char *name, ...);

#ifdef CONFIG_NUMA