linux-kernel - [PATCH 4/8] make securityfs_remove() remove the entire subtree

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Message-ID: <20250509043937.GO2023217@ZenIV>
Date: Fri, 9 May 2025 05:39:37 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: alexjlzheng@...il.com
Cc: paul@...l-moore.com, jmorris@...ei.org, serge@...lyn.com,
	greg@...ah.com, chrisw@...l.org,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jinliang Zheng <alexjlzheng@...cent.com>
Subject: [PATCH 4/8] make securityfs_remove() remove the entire subtree

>From 7b5a69f41094b9a4aff491d00e9b8515fa248cef Mon Sep 17 00:00:00 2001
From: Al Viro <viro@...iv.linux.org.uk>
Date: Mon, 13 May 2024 23:36:53 -0600
Subject: [PATCH 4/8] make securityfs_remove() remove the entire subtree

... and fix the mount leak when anything's mounted there.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 security/inode.c | 47 +++++++++++++----------------------------------
 1 file changed, 13 insertions(+), 34 deletions(-)

diff --git a/security/inode.c b/security/inode.c
index 19ab99feeee3..7604040d5c45 100644
--- a/security/inode.c
+++ b/security/inode.c
@@ -281,6 +281,12 @@ struct dentry *securityfs_create_symlink(const char *name,
 }
 EXPORT_SYMBOL_GPL(securityfs_create_symlink);
 
+static void remove_one(struct dentry *victim)
+{
+	if (victim->d_parent != victim->d_sb->s_root)
+		simple_release_fs(&mount, &mount_count);
+}
+
 /**
  * securityfs_remove - removes a file or directory from the securityfs filesystem
  *
@@ -293,51 +299,24 @@ EXPORT_SYMBOL_GPL(securityfs_create_symlink);
  * This function is required to be called in order for the file to be
  * removed. No automatic cleanup of files will happen when a module is
  * removed; you are responsible here.
+ *
+ * AV: when applied to directory it will take all children out; no need to call
+ * it for descendents if ancestor is getting killed.
  */
 void securityfs_remove(struct dentry *dentry)
 {
-	struct inode *dir;
-
 	if (IS_ERR_OR_NULL(dentry))
 		return;
 
-	dir = d_inode(dentry->d_parent);
-	inode_lock(dir);
-	if (simple_positive(dentry)) {
-		if (d_is_dir(dentry))
-			simple_rmdir(dir, dentry);
-		else
-			simple_unlink(dir, dentry);
-	}
-	inode_unlock(dir);
-	if (dir != dir->i_sb->s_root->d_inode)
-		simple_release_fs(&mount, &mount_count);
+	simple_pin_fs(&fs_type, &mount, &mount_count);
+	simple_recursive_removal(dentry, remove_one);
+	simple_release_fs(&mount, &mount_count);
 }
 EXPORT_SYMBOL_GPL(securityfs_remove);
 
-static void remove_one(struct dentry *victim)
-{
-	if (victim->d_parent != victim->d_sb->s_root)
-		simple_release_fs(&mount, &mount_count);
-}
-
-/**
- * securityfs_recursive_remove - recursively removes a file or directory
- *
- * @dentry: a pointer to a the dentry of the file or directory to be removed.
- *
- * This function recursively removes a file or directory in securityfs that was
- * previously created with a call to another securityfs function (like
- * securityfs_create_file() or variants thereof.)
- */
 void securityfs_recursive_remove(struct dentry *dentry)
 {
-	if (IS_ERR_OR_NULL(dentry))
-		return;
-
-	simple_pin_fs(&fs_type, &mount, &mount_count);
-	simple_recursive_removal(dentry, remove_one);
-	simple_release_fs(&mount, &mount_count);
+	securityfs_remove(dentry);
 }
 EXPORT_SYMBOL_GPL(securityfs_recursive_remove);
 
-- 
2.39.5