Merge patch series "VFS: improve interface for lookup_one functions"

NeilBrown <neil@brown.name> says:

VFS has some functions with names containing "lookup_one_len" and others
without the "_len".  This difference has nothing to do with "len".  This
is an historical accident but can be confusing.

The functions without "_len" take a "mnt_idmap" pointer.  This is found
in the "vfsmount" and that is an important question when choosing which
to use: do you have a vfsmount, or are you "inside" the filesystem.  A
related question is "is permission checking relevant here?".

nfsd and cachefiles *do* have a vfsmount but *don't* use the non-_len
functions.  They pass nop_mnt_idmap and refuse to work on filesystems
which have any other idmap.

This series changes nfsd and cachefile to use the lookup_one family of
functions and to explictily pass &nop_mnt_idmap which is consistent with
all other vfs interfaces used where &nop_mnt_idmap is explicitly passed.

The remaining uses of the "_one" functions do not require permission
checks so these are renamed to be "_noperm" and the permission checking
is removed.

This series also changes these lookup function to take a qstr instead of
separate name and len.  In many cases this simplifies the call.

* patches from https://lore.kernel.org/r/20250319031545.2999807-2-neil@brown.name:
  VFS: change lookup_one_common and lookup_noperm_common to take a qstr
  Use try_lookup_noperm() instead of d_hash_and_lookup() outside of VFS
  VFS: rename lookup_one_len family to lookup_noperm and remove permission check
  cachefiles: Use lookup_one() rather than lookup_one_len()
  nfsd: Use lookup_one() rather than lookup_one_len()
  VFS: improve interface for lookup_one functions

Link: https://lore.kernel.org/r/20250319031545.2999807-2-neil@brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>

3 files changed, 5 insertions, 5 deletions

diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
index 6039afae4bfc..0aef34b9609b 100644
--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c
@@ -283,7 +283,7 @@ static struct dentry *aafs_create(const char *name, umode_t mode,
 	dir = d_inode(parent);
 
 	inode_lock(dir);
-	dentry = lookup_one_len(name, parent, strlen(name));
+	dentry = lookup_noperm(&QSTR(name), parent);
 	if (IS_ERR(dentry)) {
 		error = PTR_ERR(dentry);
 		goto fail_lock;
@@ -2551,7 +2551,7 @@ static int aa_mk_null_file(struct dentry *parent)
 		return error;
 
 	inode_lock(d_inode(parent));
-	dentry = lookup_one_len(NULL_FILE_NAME, parent, strlen(NULL_FILE_NAME));
+	dentry = lookup_noperm(&QSTR(NULL_FILE_NAME), parent);
 	if (IS_ERR(dentry)) {
 		error = PTR_ERR(dentry);
 		goto out;
diff --git a/security/inode.c b/security/inode.c
index da3ab44c8e57..3913501621fa 100644
--- a/security/inode.c
+++ b/security/inode.c
@@ -128,7 +128,7 @@ static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
 	dir = d_inode(parent);
 
 	inode_lock(dir);
-	dentry = lookup_one_len(name, parent, strlen(name));
+	dentry = lookup_noperm(&QSTR(name), parent);
 	if (IS_ERR(dentry))
 		goto out;
 
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 47480eb2189b..e67a8ce4b64c 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -2158,8 +2158,8 @@ static int __init init_sel_fs(void)
 		return err;
 	}
 
-	selinux_null.dentry = d_hash_and_lookup(selinux_null.mnt->mnt_root,
-						&null_name);
+	selinux_null.dentry = try_lookup_noperm(&null_name,
+						  selinux_null.mnt->mnt_root);
 	if (IS_ERR(selinux_null.dentry)) {
 		pr_err("selinuxfs:  could not lookup null!\n");
 		err = PTR_ERR(selinux_null.dentry);