[PATCH 5.10 28/79] debugfs: add debugfs_lookup_and_remove()

Greg Kroah-Hartman
2022-09-13T14:53:34Z

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit dec9b2f1e0455a151a7293c367da22ab973f713e upstream.

There is a very common pattern of using
debugfs_remove(debufs_lookup(..)) which results in a dentry leak of the
dentry that was looked up. Instead of having to open-code the correct
pattern of calling dput() on the dentry, create
debugfs_lookup_and_remove() to handle this pattern automatically and
properly without any memory leaks.

Cc: stable <stable@kernel.org>
Reported-by: Kuyo Chang <kuyo.chang@mediatek.com>
Tested-by: Kuyo Chang <kuyo.chang@mediatek.com>
Link: https://lore.kernel.org/r/YxIaQ8cSinDR881k@kroah.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/debugfs/inode.c | 22 ++++++++++++++++++++++
include/linux/debugfs.h | 6 ++++++
2 files changed, 28 insertions(+)

--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -731,6 +731,28 @@ void debugfs_remove(struct dentry *dentr
EXPORT_SYMBOL_GPL(debugfs_remove);

/**
+ * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
+ * @name: a pointer to a string containing the name of the item to look up.
+ * @parent: a pointer to the parent dentry of the item.
+ *
+ * This is the equlivant of doing something like
+ * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
+ * handled for the directory being looked up.
+ */
+void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
+{
+ struct dentry *dentry;
+
+ dentry = debugfs_lookup(name, parent);
+ if (!dentry)
+ return;
+
+ debugfs_remove(dentry);
+ dput(dentry);
+}
+EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
+
+/**
* debugfs_rename - rename a file/directory in the debugfs filesystem
* @old_dir: a pointer to the parent dentry for the renamed object. This
* should be a directory dentry.
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -91,6 +91,8 @@ struct dentry *debugfs_create_automount(
void debugfs_remove(struct dentry *dentry);
#define debugfs_remove_recursive debugfs_remove

+void debugfs_lookup_and_remove(const char *name, struct dentry *parent);
+
const struct file_operations *debugfs_real_fops(const struct file *filp);

int debugfs_file_get(struct dentry *dentry);
@@ -220,6 +222,10 @@ static inline void debugfs_remove(struct
static inline void debugfs_remove_recursive(struct dentry *dentry)
{ }

+static inline void debugfs_lookup_and_remove(const char *name,
+ struct dentry *parent)
+{ }
+
const struct file_operations *debugfs_real_fops(const struct file *filp);

static inline int debugfs_file_get(struct dentry *dentry)