fs: port vfs_*() helpers to struct mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

1 files changed, 27 insertions, 20 deletions

diff --git a/fs/ksmbd/vfs.c b/fs/ksmbd/vfs.c
index ff0e7a4fcd4d..5b284dd61056 100644
--- a/fs/ksmbd/vfs.c
+++ b/fs/ksmbd/vfs.c
@@ -177,7 +177,7 @@ int ksmbd_vfs_create(struct ksmbd_work *work, const char *name, umode_t mode)
 	}
 
 	mode |= S_IFREG;
-	err = vfs_create(mnt_user_ns(path.mnt), d_inode(path.dentry),
+	err = vfs_create(mnt_idmap(path.mnt), d_inode(path.dentry),
 			 dentry, mode, true);
 	if (!err) {
 		ksmbd_vfs_inherit_owner(work, d_inode(path.dentry),
@@ -199,6 +199,7 @@ int ksmbd_vfs_create(struct ksmbd_work *work, const char *name, umode_t mode)
  */
 int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char *name, umode_t mode)
 {
+	struct mnt_idmap *idmap;
 	struct user_namespace *user_ns;
 	struct path path;
 	struct dentry *dentry;
@@ -215,9 +216,10 @@ int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char *name, umode_t mode)
 		return err;
 	}
 
-	user_ns = mnt_user_ns(path.mnt);
+	idmap = mnt_idmap(path.mnt);
+	user_ns = mnt_idmap_owner(idmap);
 	mode |= S_IFDIR;
-	err = vfs_mkdir(user_ns, d_inode(path.dentry), dentry, mode);
+	err = vfs_mkdir(idmap, d_inode(path.dentry), dentry, mode);
 	if (err) {
 		goto out;
 	} else if (d_unhashed(dentry)) {
@@ -583,6 +585,7 @@ int ksmbd_vfs_fsync(struct ksmbd_work *work, u64 fid, u64 p_id)
  */
 int ksmbd_vfs_remove_file(struct ksmbd_work *work, char *name)
 {
+	struct mnt_idmap *idmap;
 	struct user_namespace *user_ns;
 	struct path path;
 	struct dentry *parent;
@@ -598,7 +601,8 @@ int ksmbd_vfs_remove_file(struct ksmbd_work *work, char *name)
 		return err;
 	}
 
-	user_ns = mnt_user_ns(path.mnt);
+	idmap = mnt_idmap(path.mnt);
+	user_ns = mnt_idmap_owner(idmap);
 	parent = dget_parent(path.dentry);
 	err = ksmbd_vfs_lock_parent(user_ns, parent, path.dentry);
 	if (err) {
@@ -614,12 +618,12 @@ int ksmbd_vfs_remove_file(struct ksmbd_work *work, char *name)
 	}
 
 	if (S_ISDIR(d_inode(path.dentry)->i_mode)) {
-		err = vfs_rmdir(user_ns, d_inode(parent), path.dentry);
+		err = vfs_rmdir(idmap, d_inode(parent), path.dentry);
 		if (err && err != -ENOTEMPTY)
 			ksmbd_debug(VFS, "%s: rmdir failed, err %d\n", name,
 				    err);
 	} else {
-		err = vfs_unlink(user_ns, d_inode(parent), path.dentry, NULL);
+		err = vfs_unlink(idmap, d_inode(parent), path.dentry, NULL);
 		if (err)
 			ksmbd_debug(VFS, "%s: unlink failed, err %d\n", name,
 				    err);
@@ -672,7 +676,7 @@ int ksmbd_vfs_link(struct ksmbd_work *work, const char *oldname,
 		goto out3;
 	}
 
-	err = vfs_link(oldpath.dentry, mnt_user_ns(newpath.mnt),
+	err = vfs_link(oldpath.dentry, mnt_idmap(newpath.mnt),
 		       d_inode(newpath.dentry),
 		       dentry, NULL);
 	if (err)
@@ -711,10 +715,10 @@ static int ksmbd_validate_entry_in_use(struct dentry *src_dent)
 }
 
 static int __ksmbd_vfs_rename(struct ksmbd_work *work,
-			      struct user_namespace *src_user_ns,
+			      struct mnt_idmap *src_idmap,
 			      struct dentry *src_dent_parent,
 			      struct dentry *src_dent,
-			      struct user_namespace *dst_user_ns,
+			      struct mnt_idmap *dst_idmap,
 			      struct dentry *dst_dent_parent,
 			      struct dentry *trap_dent,
 			      char *dst_name)
@@ -740,8 +744,8 @@ static int __ksmbd_vfs_rename(struct ksmbd_work *work,
 	if (ksmbd_override_fsids(work))
 		return -ENOMEM;
 
-	dst_dent = lookup_one(dst_user_ns, dst_name, dst_dent_parent,
-			      strlen(dst_name));
+	dst_dent = lookup_one(mnt_idmap_owner(dst_idmap), dst_name,
+			      dst_dent_parent, strlen(dst_name));
 	err = PTR_ERR(dst_dent);
 	if (IS_ERR(dst_dent)) {
 		pr_err("lookup failed %s [%d]\n", dst_name, err);
@@ -751,10 +755,10 @@ static int __ksmbd_vfs_rename(struct ksmbd_work *work,
 	err = -ENOTEMPTY;
 	if (dst_dent != trap_dent && !d_really_is_positive(dst_dent)) {
 		struct renamedata rd = {
-			.old_mnt_userns	= src_user_ns,
+			.old_mnt_idmap	= src_idmap,
 			.old_dir	= d_inode(src_dent_parent),
 			.old_dentry	= src_dent,
-			.new_mnt_userns	= dst_user_ns,
+			.new_mnt_idmap	= dst_idmap,
 			.new_dir	= d_inode(dst_dent_parent),
 			.new_dentry	= dst_dent,
 		};
@@ -772,6 +776,7 @@ out:
 int ksmbd_vfs_fp_rename(struct ksmbd_work *work, struct ksmbd_file *fp,
 			char *newname)
 {
+	struct mnt_idmap *idmap;
 	struct user_namespace *user_ns;
 	struct path dst_path;
 	struct dentry *src_dent_parent, *dst_dent_parent;
@@ -800,7 +805,8 @@ int ksmbd_vfs_fp_rename(struct ksmbd_work *work, struct ksmbd_file *fp,
 	trap_dent = lock_rename(src_dent_parent, dst_dent_parent);
 	dget(src_dent);
 	dget(dst_dent_parent);
-	user_ns = file_mnt_user_ns(fp->filp);
+	idmap = file_mnt_idmap(fp->filp);
+	user_ns = mnt_idmap_owner(idmap);
 	src_child = lookup_one(user_ns, src_dent->d_name.name, src_dent_parent,
 			       src_dent->d_name.len);
 	if (IS_ERR(src_child)) {
@@ -816,10 +822,10 @@ int ksmbd_vfs_fp_rename(struct ksmbd_work *work, struct ksmbd_file *fp,
 	dput(src_child);
 
 	err = __ksmbd_vfs_rename(work,
-				 user_ns,
+				 idmap,
 				 src_dent_parent,
 				 src_dent,
-				 mnt_user_ns(dst_path.mnt),
+				 mnt_idmap(dst_path.mnt),
 				 dst_dent_parent,
 				 trap_dent,
 				 dst_name);
@@ -1080,20 +1086,21 @@ int ksmbd_vfs_remove_xattr(struct user_namespace *user_ns,
 	return vfs_removexattr(user_ns, dentry, attr_name);
 }
 
-int ksmbd_vfs_unlink(struct user_namespace *user_ns,
+int ksmbd_vfs_unlink(struct mnt_idmap *idmap,
 		     struct dentry *dir, struct dentry *dentry)
 {
 	int err = 0;
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 
-	err = ksmbd_vfs_lock_parent(user_ns, dir, dentry);
+	err = ksmbd_vfs_lock_parent(mnt_userns, dir, dentry);
 	if (err)
 		return err;
 	dget(dentry);
 
 	if (S_ISDIR(d_inode(dentry)->i_mode))
-		err = vfs_rmdir(user_ns, d_inode(dir), dentry);
+		err = vfs_rmdir(idmap, d_inode(dir), dentry);
 	else
-		err = vfs_unlink(user_ns, d_inode(dir), dentry, NULL);
+		err = vfs_unlink(idmap, d_inode(dir), dentry, NULL);
 
 	dput(dentry);
 	inode_unlock(d_inode(dir));