VFS: rename lookup_one_len family to lookup_noperm and remove permission check

The lookup_one_len family of functions is (now) only used internally by
a filesystem on itself either
- in a context where permission checking is irrelevant such as by a
  virtual filesystem populating itself, or xfs accessing its ORPHANAGE
  or dquota accessing the quota file; or
- in a context where a permission check (MAY_EXEC on the parent) has just
  been performed such as a network filesystem finding in "silly-rename"
  file in the same directory.  This is also the context after the
  _parentat() functions where currently lookup_one_qstr_excl() is used.

So the permission check is pointless.

The name "one_len" is unhelpful in understanding the purpose of these
functions and should be changed.  Most of the callers pass the len as
"strlen()" so using a qstr and QSTR() can simplify the code.

This patch renames these functions (include lookup_positive_unlocked()
which is part of the family despite the name) to have a name based on
"lookup_noperm".  They are changed to receive a 'struct qstr' instead
of separate name and len.  In a few cases the use of QSTR() results in a
new call to strlen().

try_lookup_noperm() takes a pointer to a qstr instead of the whole
qstr.  This is consistent with d_hash_and_lookup() (which is nearly
identical) and useful for lookup_noperm_unlocked().

The new lookup_noperm_common() doesn't take a qstr yet.  That will be
tidied up in a subsequent patch.

Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/r/20250319031545.2999807-5-neil@brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index 94c6446604fc..98da8c4eea59 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -187,7 +187,7 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
 	inode_lock(d_inode(root));
 
 	/* look it up */
-	dentry = lookup_one_len(name, root, name_len);
+	dentry = lookup_noperm(&QSTR(name), root);
 	if (IS_ERR(dentry)) {
 		inode_unlock(d_inode(root));
 		ret = PTR_ERR(dentry);
@@ -487,7 +487,7 @@ static struct dentry *binderfs_create_dentry(struct dentry *parent,
 {
 	struct dentry *dentry;
 
-	dentry = lookup_one_len(name, parent, strlen(name));
+	dentry = lookup_noperm(&QSTR(name), parent);
 	if (IS_ERR(dentry))
 		return dentry;