Patch "gpio: virtuser: lock up configfs that an instantiated device depends on" has been added to the 6.12-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    gpio: virtuser: lock up configfs that an instantiated device depends on

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     gpio-virtuser-lock-up-configfs-that-an-instantiated-.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3fbd41c833cdc4b0867f1b6873f43ab5fb255f48
Author: Koichiro Den <koichiro.den@xxxxxxxxxxxxx>
Date:   Fri Jan 3 23:18:28 2025 +0900

    gpio: virtuser: lock up configfs that an instantiated device depends on
    
    [ Upstream commit c7c434c1dba955005f5161dae73f09c0a922cfa7 ]
    
    Once a virtuser device is instantiated and actively used, allowing rmdir
    for its configfs serves no purpose and can be confusing. Userspace
    interacts with the virtual consumer at arbitrary times, meaning it
    depends on its existence.
    
    Make the subsystem itself depend on the configfs entry for a virtuser
    device while it is in active use.
    
    Signed-off-by: Koichiro Den <koichiro.den@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20250103141829.430662-4-koichiro.den@xxxxxxxxxxxxx
    Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/gpio/gpio-virtuser.c b/drivers/gpio/gpio-virtuser.c
index d6244f0d3bc75..e89f299f21400 100644
--- a/drivers/gpio/gpio-virtuser.c
+++ b/drivers/gpio/gpio-virtuser.c
@@ -1546,6 +1546,30 @@ gpio_virtuser_device_deactivate(struct gpio_virtuser_device *dev)
 	dev->pdev = NULL;
 }
 
+static void
+gpio_virtuser_device_lockup_configfs(struct gpio_virtuser_device *dev, bool lock)
+{
+	struct configfs_subsystem *subsys = dev->group.cg_subsys;
+	struct gpio_virtuser_lookup_entry *entry;
+	struct gpio_virtuser_lookup *lookup;
+
+	/*
+	 * The device only needs to depend on leaf lookup entries. This is
+	 * sufficient to lock up all the configfs entries that the
+	 * instantiated, alive device depends on.
+	 */
+	list_for_each_entry(lookup, &dev->lookup_list, siblings) {
+		list_for_each_entry(entry, &lookup->entry_list, siblings) {
+			if (lock)
+				WARN_ON(configfs_depend_item_unlocked(
+						subsys, &entry->group.cg_item));
+			else
+				configfs_undepend_item_unlocked(
+						&entry->group.cg_item);
+		}
+	}
+}
+
 static ssize_t
 gpio_virtuser_device_config_live_store(struct config_item *item,
 				       const char *page, size_t count)
@@ -1558,15 +1582,24 @@ gpio_virtuser_device_config_live_store(struct config_item *item,
 	if (ret)
 		return ret;
 
-	guard(mutex)(&dev->lock);
+	if (live)
+		gpio_virtuser_device_lockup_configfs(dev, true);
 
-	if (live == gpio_virtuser_device_is_live(dev))
-		return -EPERM;
+	scoped_guard(mutex, &dev->lock) {
+		if (live == gpio_virtuser_device_is_live(dev))
+			ret = -EPERM;
+		else if (live)
+			ret = gpio_virtuser_device_activate(dev);
+		else
+			gpio_virtuser_device_deactivate(dev);
+	}
 
-	if (live)
-		ret = gpio_virtuser_device_activate(dev);
-	else
-		gpio_virtuser_device_deactivate(dev);
+	/*
+	 * Undepend is required only if device disablement (live == 0)
+	 * succeeds or if device enablement (live == 1) fails.
+	 */
+	if (live == !!ret)
+		gpio_virtuser_device_lockup_configfs(dev, false);
 
 	return ret ?: count;
 }