4 files changed, 60 insertions, 49 deletions
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index c9993ff66fc2..fe493f3ed6b6 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -138,37 +138,6 @@ kill_whiteout:
 	goto out;
 }
 
-int ovl_mkdir_real(struct ovl_fs *ofs, struct inode *dir,
-		   struct dentry **newdentry, umode_t mode)
-{
-	int err;
-	struct dentry *d, *dentry = *newdentry;
-
-	err = ovl_do_mkdir(ofs, dir, dentry, mode);
-	if (err)
-		return err;
-
-	if (likely(!d_unhashed(dentry)))
-		return 0;
-
-	/*
-	 * vfs_mkdir() may succeed and leave the dentry passed
-	 * to it unhashed and negative. If that happens, try to
-	 * lookup a new hashed and positive dentry.
-	 */
-	d = ovl_lookup_upper(ofs, dentry->d_name.name, dentry->d_parent,
-			     dentry->d_name.len);
-	if (IS_ERR(d)) {
-		pr_warn("failed lookup after mkdir (%pd2, err=%i).\n",
-			dentry, err);
-		return PTR_ERR(d);
-	}
-	dput(dentry);
-	*newdentry = d;
-
-	return 0;
-}
-
 struct dentry *ovl_create_real(struct ovl_fs *ofs, struct inode *dir,
 			       struct dentry *newdentry, struct ovl_cattr *attr)
 {
@@ -191,7 +160,8 @@ struct dentry *ovl_create_real(struct ovl_fs *ofs, struct inode *dir,
 
 		case S_IFDIR:
 			/* mkdir is special... */
-			err =  ovl_mkdir_real(ofs, dir, &newdentry, attr->mode);
+			newdentry =  ovl_do_mkdir(ofs, dir, newdentry, attr->mode);
+			err = PTR_ERR_OR_ZERO(newdentry);
 			break;
 
 		case S_IFCHR:
@@ -219,7 +189,8 @@ struct dentry *ovl_create_real(struct ovl_fs *ofs, struct inode *dir,
 	}
 out:
 	if (err) {
-		dput(newdentry);
+		if (!IS_ERR(newdentry))
+			dput(newdentry);
 		return ERR_PTR(err);
 	}
 	return newdentry;
@@ -282,7 +253,8 @@ static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
 		 * XXX: if we ever use ovl_obtain_alias() to decode directory
 		 * file handles, need to use ovl_get_inode_locked() and
 		 * d_instantiate_new() here to prevent from creating two
-		 * hashed directory inode aliases.
+		 * hashed directory inode aliases.  We then need to return
+		 * the obtained alias to ovl_mkdir().
 		 */
 		inode = ovl_get_inode(dentry->d_sb, &oip);
 		if (IS_ERR(inode))
@@ -687,10 +659,10 @@ static int ovl_create(struct mnt_idmap *idmap, struct inode *dir,
 	return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
 }
 
-static int ovl_mkdir(struct mnt_idmap *idmap, struct inode *dir,
-		     struct dentry *dentry, umode_t mode)
+static struct dentry *ovl_mkdir(struct mnt_idmap *idmap, struct inode *dir,
+				struct dentry *dentry, umode_t mode)
 {
-	return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
+	return ERR_PTR(ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL));
 }
 
 static int ovl_mknod(struct mnt_idmap *idmap, struct inode *dir,
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 0021e2025020..6f2f8f4cfbbc 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -241,13 +241,14 @@ static inline int ovl_do_create(struct ovl_fs *ofs,
 	return err;
 }
 
-static inline int ovl_do_mkdir(struct ovl_fs *ofs,
-			       struct inode *dir, struct dentry *dentry,
-			       umode_t mode)
+static inline struct dentry *ovl_do_mkdir(struct ovl_fs *ofs,
+					  struct inode *dir,
+					  struct dentry *dentry,
+					  umode_t mode)
 {
-	int err = vfs_mkdir(ovl_upper_mnt_idmap(ofs), dir, dentry, mode);
-	pr_debug("mkdir(%pd2, 0%o) = %i\n", dentry, mode, err);
-	return err;
+	dentry = vfs_mkdir(ovl_upper_mnt_idmap(ofs), dir, dentry, mode);
+	pr_debug("mkdir(%pd2, 0%o) = %i\n", dentry, mode, PTR_ERR_OR_ZERO(dentry));
+	return dentry;
 }
 
 static inline int ovl_do_mknod(struct ovl_fs *ofs,
@@ -838,8 +839,6 @@ struct ovl_cattr {
 
 #define OVL_CATTR(m) (&(struct ovl_cattr) { .mode = (m) })
 
-int ovl_mkdir_real(struct ovl_fs *ofs, struct inode *dir,
-		   struct dentry **newdentry, umode_t mode);
 struct dentry *ovl_create_real(struct ovl_fs *ofs,
 			       struct inode *dir, struct dentry *newdentry,
 			       struct ovl_cattr *attr);
diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index 1115c22deca0..6759f7d040c8 100644
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -59,6 +59,7 @@ enum ovl_opt {
 	Opt_metacopy,
 	Opt_verity,
 	Opt_volatile,
+	Opt_override_creds,
 };
 
 static const struct constant_table ovl_parameter_bool[] = {
@@ -155,6 +156,7 @@ const struct fs_parameter_spec ovl_parameter_spec[] = {
 	fsparam_enum("metacopy",            Opt_metacopy, ovl_parameter_bool),
 	fsparam_enum("verity",              Opt_verity, ovl_parameter_verity),
 	fsparam_flag("volatile",            Opt_volatile),
+	fsparam_flag_no("override_creds",   Opt_override_creds),
 	{}
 };
 
@@ -662,6 +664,29 @@ static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
 	case Opt_userxattr:
 		config->userxattr = true;
 		break;
+	case Opt_override_creds: {
+		const struct cred *cred = NULL;
+
+		if (result.negated) {
+			swap(cred, ofs->creator_cred);
+			put_cred(cred);
+			break;
+		}
+
+		if (!current_in_userns(fc->user_ns)) {
+			err = -EINVAL;
+			break;
+		}
+
+		cred = prepare_creds();
+		if (cred)
+			swap(cred, ofs->creator_cred);
+		else
+			err = -ENOMEM;
+
+		put_cred(cred);
+		break;
+	}
 	default:
 		pr_err("unrecognized mount option \"%s\" or missing value\n",
 		       param->key);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 86ae6f6da36b..b63474d1b064 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -327,9 +327,10 @@ retry:
 			goto retry;
 		}
 
-		err = ovl_mkdir_real(ofs, dir, &work, attr.ia_mode);
-		if (err)
-			goto out_dput;
+		work = ovl_do_mkdir(ofs, dir, work, attr.ia_mode);
+		err = PTR_ERR(work);
+		if (IS_ERR(work))
+			goto out_err;
 
 		/* Weird filesystem returning with hashed negative (kernfs)? */
 		err = -EINVAL;
@@ -1305,6 +1306,7 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct ovl_fs *ofs = sb->s_fs_info;
 	struct ovl_fs_context *ctx = fc->fs_private;
+	const struct cred *old_cred = NULL;
 	struct dentry *root_dentry;
 	struct ovl_entry *oe;
 	struct ovl_layer *layers;
@@ -1318,10 +1320,15 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
 	sb->s_d_op = &ovl_dentry_operations;
 
 	err = -ENOMEM;
-	ofs->creator_cred = cred = prepare_creds();
+	if (!ofs->creator_cred)
+		ofs->creator_cred = cred = prepare_creds();
+	else
+		cred = (struct cred *)ofs->creator_cred;
 	if (!cred)
 		goto out_err;
 
+	old_cred = ovl_override_creds(sb);
+
 	err = ovl_fs_params_verify(ctx, &ofs->config);
 	if (err)
 		goto out_err;
@@ -1481,11 +1488,19 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
 
 	sb->s_root = root_dentry;
 
+	ovl_revert_creds(old_cred);
 	return 0;
 
 out_free_oe:
 	ovl_free_entry(oe);
 out_err:
+	/*
+	 * Revert creds before calling ovl_free_fs() which will call
+	 * put_cred() and put_cred() requires that the cred's that are
+	 * put are not the caller's creds, i.e., current->cred.
+	 */
+	if (old_cred)
+		ovl_revert_creds(old_cred);
 	ovl_free_fs(ofs);
 	sb->s_fs_info = NULL;
 	return err;