Use try_lookup_noperm() instead of d_hash_and_lookup() outside of VFS

try_lookup_noperm() and d_hash_and_lookup() are nearly identical.  The
former does some validation of the name where the latter doesn't.
Outside of the VFS that validation is likely valuable, and having only
one exported function for this task is certainly a good idea.

So make d_hash_and_lookup() local to VFS files and change all other
callers to try_lookup_noperm().  Note that the arguments are swapped.

Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250319031545.2999807-6-neil@brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>

6 files changed, 11 insertions, 15 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index bd5aa136153a..89f4acab08c0 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2412,7 +2412,6 @@ struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
 	}
 	return d_lookup(dir, name);
 }
-EXPORT_SYMBOL(d_hash_and_lookup);
 
 /*
  * When a file is deleted, we have two options:
diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
index 0486e9b68bc6..b2de4079864c 100644
--- a/fs/efivarfs/super.c
+++ b/fs/efivarfs/super.c
@@ -18,6 +18,7 @@
 #include <linux/statfs.h>
 #include <linux/notifier.h>
 #include <linux/printk.h>
+#include <linux/namei.h>
 
 #include "internal.h"
 
@@ -204,7 +205,6 @@ bool efivarfs_variable_is_present(efi_char16_t *variable_name,
 	char *name = efivar_get_utf8name(variable_name, vendor);
 	struct super_block *sb = data;
 	struct dentry *dentry;
-	struct qstr qstr;
 
 	if (!name)
 		/*
@@ -217,9 +217,7 @@ bool efivarfs_variable_is_present(efi_char16_t *variable_name,
 		 */
 		return true;
 
-	qstr.name = name;
-	qstr.len = strlen(name);
-	dentry = d_hash_and_lookup(sb->s_root, &qstr);
+	dentry = try_lookup_noperm(&QSTR(name), sb->s_root);
 	kfree(name);
 	if (!IS_ERR_OR_NULL(dentry))
 		dput(dentry);
@@ -404,8 +402,8 @@ static bool efivarfs_actor(struct dir_context *ctx, const char *name, int len,
 {
 	unsigned long size;
 	struct efivarfs_ctx *ectx = container_of(ctx, struct efivarfs_ctx, ctx);
-	struct qstr qstr = { .name = name, .len = len };
-	struct dentry *dentry = d_hash_and_lookup(ectx->sb->s_root, &qstr);
+	struct dentry *dentry = try_lookup_noperm(&QSTR_LEN(name, len),
+						  ectx->sb->s_root);
 	struct inode *inode;
 	struct efivar_entry *entry;
 	int err;
@@ -441,7 +439,6 @@ static int efivarfs_check_missing(efi_char16_t *name16, efi_guid_t vendor,
 	char *name;
 	struct super_block *sb = data;
 	struct dentry *dentry;
-	struct qstr qstr;
 	int err;
 
 	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
@@ -451,9 +448,7 @@ static int efivarfs_check_missing(efi_char16_t *name16, efi_guid_t vendor,
 	if (!name)
 		return -ENOMEM;
 
-	qstr.name = name;
-	qstr.len = strlen(name);
-	dentry = d_hash_and_lookup(sb->s_root, &qstr);
+	dentry = try_lookup_noperm(&QSTR(name), sb->s_root);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		goto out;
diff --git a/fs/internal.h b/fs/internal.h
index b9b3e29a73fd..213bf3226213 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -66,6 +66,7 @@ int do_linkat(int olddfd, struct filename *old, int newdfd,
 int vfs_tmpfile(struct mnt_idmap *idmap,
 		const struct path *parentpath,
 		struct file *file, umode_t mode);
+struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 
 /*
  * namespace.c
diff --git a/fs/proc/base.c b/fs/proc/base.c
index b0d4e1908b22..fe33a5843fbd 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2121,7 +2121,7 @@ bool proc_fill_cache(struct file *file, struct dir_context *ctx,
 	unsigned type = DT_UNKNOWN;
 	ino_t ino = 1;
 
-	child = d_hash_and_lookup(dir, &qname);
+	child = try_lookup_noperm(&qname, dir);
 	if (!child) {
 		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
 		child = d_alloc_parallel(dir, &qname, &wq);
diff --git a/fs/smb/client/readdir.c b/fs/smb/client/readdir.c
index 50f96259d9ad..7329ec532bcf 100644
--- a/fs/smb/client/readdir.c
+++ b/fs/smb/client/readdir.c
@@ -9,6 +9,7 @@
  *
  */
 #include <linux/fs.h>
+#include <linux/namei.h>
 #include <linux/pagemap.h>
 #include <linux/slab.h>
 #include <linux/stat.h>
@@ -78,7 +79,7 @@ cifs_prime_dcache(struct dentry *parent, struct qstr *name,
 
 	cifs_dbg(FYI, "%s: for %s\n", __func__, name->name);
 
-	dentry = d_hash_and_lookup(parent, name);
+	dentry = try_lookup_noperm(name, parent);
 	if (!dentry) {
 		/*
 		 * If we know that the inode will need to be revalidated
diff --git a/fs/xfs/scrub/orphanage.c b/fs/xfs/scrub/orphanage.c
index 475bb899b2c6..9c12cb844231 100644
--- a/fs/xfs/scrub/orphanage.c
+++ b/fs/xfs/scrub/orphanage.c
@@ -444,7 +444,7 @@ xrep_adoption_check_dcache(
 	if (!d_orphanage)
 		return 0;
 
-	d_child = d_hash_and_lookup(d_orphanage, &qname);
+	d_child = try_lookup_noperm(&qname, d_orphanage);
 	if (d_child) {
 		trace_xrep_adoption_check_child(sc->mp, d_child);
 
@@ -481,7 +481,7 @@ xrep_adoption_zap_dcache(
 	if (!d_orphanage)
 		return;
 
-	d_child = d_hash_and_lookup(d_orphanage, &qname);
+	d_child = try_lookup_noperm(&qname, d_orphanage);
 	while (d_child != NULL) {
 		trace_xrep_adoption_invalidate_child(sc->mp, d_child);