[PATCH 1/2] VFS: change kern_path_locked() and user_path_locked_at() to never return negative dentry

[NeilBrown <neilb@suse.de>]

No callers of kern_path_locked() or user_path_locked_at() want a
negative dentry.  So change them to return -ENOENT instead.  This
simplifies callers.

This results in a subtle change to bcachefs in that an ioctl will now
return -ENOENT in preference to -EXDEV.  I believe this restores the
behaviour to what it was prior to
 Commit bbe6a7c899e7 ("bch2_ioctl_subvolume_destroy(): fix locking")

Signed-off-by: NeilBrown <neilb@suse.de>
---
 drivers/base/devtmpfs.c | 65 +++++++++++++++++++----------------------
 fs/bcachefs/fs-ioctl.c  |  4 ---
 fs/namei.c              |  4 +++
 kernel/audit_watch.c    | 12 ++++----
 4 files changed, 40 insertions(+), 45 deletions(-)

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index b848764ef018..c9e34842139f 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -245,15 +245,12 @@ static int dev_rmdir(const char *name)
 	dentry = kern_path_locked(name, &parent);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
-	if (d_really_is_positive(dentry)) {
-		if (d_inode(dentry)->i_private == &thread)
-			err = vfs_rmdir(&nop_mnt_idmap, d_inode(parent.dentry),
-					dentry);
-		else
-			err = -EPERM;
-	} else {
-		err = -ENOENT;
-	}
+	if (d_inode(dentry)->i_private == &thread)
+		err = vfs_rmdir(&nop_mnt_idmap, d_inode(parent.dentry),
+				dentry);
+	else
+		err = -EPERM;
+
 	dput(dentry);
 	inode_unlock(d_inode(parent.dentry));
 	path_put(&parent);
@@ -310,6 +307,8 @@ static int handle_remove(const char *nodename, struct device *dev)
 {
 	struct path parent;
 	struct dentry *dentry;
+	struct kstat stat;
+	struct path p;
 	int deleted = 0;
 	int err;
 
@@ -317,32 +316,28 @@ static int handle_remove(const char *nodename, struct device *dev)
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
-	if (d_really_is_positive(dentry)) {
-		struct kstat stat;
-		struct path p = {.mnt = parent.mnt, .dentry = dentry};
-		err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE,
-				  AT_STATX_SYNC_AS_STAT);
-		if (!err && dev_mynode(dev, d_inode(dentry), &stat)) {
-			struct iattr newattrs;
-			/*
-			 * before unlinking this node, reset permissions
-			 * of possible references like hardlinks
-			 */
-			newattrs.ia_uid = GLOBAL_ROOT_UID;
-			newattrs.ia_gid = GLOBAL_ROOT_GID;
-			newattrs.ia_mode = stat.mode & ~0777;
-			newattrs.ia_valid =
-				ATTR_UID|ATTR_GID|ATTR_MODE;
-			inode_lock(d_inode(dentry));
-			notify_change(&nop_mnt_idmap, dentry, &newattrs, NULL);
-			inode_unlock(d_inode(dentry));
-			err = vfs_unlink(&nop_mnt_idmap, d_inode(parent.dentry),
-					 dentry, NULL);
-			if (!err || err == -ENOENT)
-				deleted = 1;
-		}
-	} else {
-		err = -ENOENT;
+	p.mnt = parent.mnt;
+	p.dentry = dentry;
+	err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE,
+			  AT_STATX_SYNC_AS_STAT);
+	if (!err && dev_mynode(dev, d_inode(dentry), &stat)) {
+		struct iattr newattrs;
+		/*
+		 * before unlinking this node, reset permissions
+		 * of possible references like hardlinks
+		 */
+		newattrs.ia_uid = GLOBAL_ROOT_UID;
+		newattrs.ia_gid = GLOBAL_ROOT_GID;
+		newattrs.ia_mode = stat.mode & ~0777;
+		newattrs.ia_valid =
+			ATTR_UID|ATTR_GID|ATTR_MODE;
+		inode_lock(d_inode(dentry));
+		notify_change(&nop_mnt_idmap, dentry, &newattrs, NULL);
+		inode_unlock(d_inode(dentry));
+		err = vfs_unlink(&nop_mnt_idmap, d_inode(parent.dentry),
+				 dentry, NULL);
+		if (!err || err == -ENOENT)
+			deleted = 1;
 	}
 	dput(dentry);
 	inode_unlock(d_inode(parent.dentry));
diff --git a/fs/bcachefs/fs-ioctl.c b/fs/bcachefs/fs-ioctl.c
index 15725b4ce393..595b57fabc9a 100644
--- a/fs/bcachefs/fs-ioctl.c
+++ b/fs/bcachefs/fs-ioctl.c
@@ -511,10 +511,6 @@ static long bch2_ioctl_subvolume_destroy(struct bch_fs *c, struct file *filp,
 		ret = -EXDEV;
 		goto err;
 	}
-	if (!d_is_positive(victim)) {
-		ret = -ENOENT;
-		goto err;
-	}
 	ret = __bch2_unlink(dir, victim, true);
 	if (!ret) {
 		fsnotify_rmdir(dir, victim);
diff --git a/fs/namei.c b/fs/namei.c
index 3a4039acdb3f..e3047db7b2b4 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2736,6 +2736,10 @@ static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct
 	}
 	inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
 	d = lookup_one_qstr_excl(&last, path->dentry, 0);
+	if (!IS_ERR(d) && d_is_negative(d)) {
+		dput(d);
+		d = ERR_PTR(-ENOENT);
+	}
 	if (IS_ERR(d)) {
 		inode_unlock(path->dentry->d_inode);
 		path_put(path);
diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c
index 7f358740e958..e3130675ee6b 100644
--- a/kernel/audit_watch.c
+++ b/kernel/audit_watch.c
@@ -350,11 +350,10 @@ static int audit_get_nd(struct audit_watch *watch, struct path *parent)
 	struct dentry *d = kern_path_locked(watch->path, parent);
 	if (IS_ERR(d))
 		return PTR_ERR(d);
-	if (d_is_positive(d)) {
-		/* update watch filter fields */
-		watch->dev = d->d_sb->s_dev;
-		watch->ino = d_backing_inode(d)->i_ino;
-	}
+	/* update watch filter fields */
+	watch->dev = d->d_sb->s_dev;
+	watch->ino = d_backing_inode(d)->i_ino;
+
 	inode_unlock(d_backing_inode(parent->dentry));
 	dput(d);
 	return 0;
@@ -419,7 +418,7 @@ int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 	/* caller expects mutex locked */
 	mutex_lock(&audit_filter_mutex);
 
-	if (ret) {
+	if (ret && ret != -ENOENT) {
 		audit_put_watch(watch);
 		return ret;
 	}
@@ -438,6 +437,7 @@ int audit_add_watch(struct audit_krule *krule, struct list_head **list)
 
 	h = audit_hash_ino((u32)watch->ino);
 	*list = &audit_inode_hash[h];
+	ret = 0;
 error:
 	path_put(&parent_path);
 	audit_put_watch(watch);
-- 
2.47.1