vboxsf: don't allow to change the inode type

vboxsf_init_inode() is used both for initial setup of inode and for metadata
updates.  Tell it whether we are updating a live inode or setting up a new
instance and have it refuse to change type in the former case.

[fixed the braino caught by Hans de Goede <hdegoede@redhat.com>]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Al Viro

fs/vboxsf/dir.c

@@ -225,7 +225,7 @@ static struct dentry *vboxsf_dir_lookup(struct inode *parent,
 	} else {
 		inode = vboxsf_new_inode(parent->i_sb);
 		if (!IS_ERR(inode))
-			vboxsf_init_inode(sbi, inode, &fsinfo);
+			vboxsf_init_inode(sbi, inode, &fsinfo, false);
 	}
 
 	return d_splice_alias(inode, dentry);
@@ -245,7 +245,7 @@ static int vboxsf_dir_instantiate(struct inode *parent, struct dentry *dentry,
 	sf_i = VBOXSF_I(inode);
 	/* The host may have given us different attr then requested */
 	sf_i->force_restat = 1;
-	vboxsf_init_inode(sbi, inode, info);
+	vboxsf_init_inode(sbi, inode, info, false);
 
 	d_instantiate(dentry, inode);
 

fs/vboxsf/super.c

@@ -207,7 +207,7 @@ static int vboxsf_fill_super(struct super_block *sb, struct fs_context *fc)
 		err = -ENOMEM;
 		goto fail_unmap;
 	}
-	vboxsf_init_inode(sbi, iroot, &sbi->root_info);
+	vboxsf_init_inode(sbi, iroot, &sbi->root_info, false);
 	unlock_new_inode(iroot);
 
 	droot = d_make_root(iroot);
@@ -418,7 +418,7 @@ static int vboxsf_reconfigure(struct fs_context *fc)
 
 	/* Apply changed options to the root inode */
 	sbi->o = ctx->o;
-	vboxsf_init_inode(sbi, iroot, &sbi->root_info);
+	vboxsf_init_inode(sbi, iroot, &sbi->root_info, true);
 
 	return 0;
 }

fs/vboxsf/utils.c

@@ -45,12 +45,12 @@ struct inode *vboxsf_new_inode(struct super_block *sb)
 }
 
 /* set [inode] attributes based on [info], uid/gid based on [sbi] */
-void vboxsf_init_inode(struct vboxsf_sbi *sbi, struct inode *inode,
-		       const struct shfl_fsobjinfo *info)
+int vboxsf_init_inode(struct vboxsf_sbi *sbi, struct inode *inode,
+		       const struct shfl_fsobjinfo *info, bool reinit)
 {
 	const struct shfl_fsobjattr *attr;
 	s64 allocated;
-	int mode;
+	umode_t mode;
 
 	attr = &info->attr;
 
@@ -75,29 +75,44 @@ void vboxsf_init_inode(struct vboxsf_sbi *sbi, struct inode *inode,
 	inode->i_mapping->a_ops = &vboxsf_reg_aops;
 
 	if (SHFL_IS_DIRECTORY(attr->mode)) {
-		inode->i_mode = sbi->o.dmode_set ? sbi->o.dmode : mode;
-		inode->i_mode &= ~sbi->o.dmask;
-		inode->i_mode |= S_IFDIR;
-		inode->i_op = &vboxsf_dir_iops;
-		inode->i_fop = &vboxsf_dir_fops;
-		/*
-		 * XXX: this probably should be set to the number of entries
-		 * in the directory plus two (. ..)
-		 */
-		set_nlink(inode, 1);
+		if (sbi->o.dmode_set)
+			mode = sbi->o.dmode;
+		mode &= ~sbi->o.dmask;
+		mode |= S_IFDIR;
+		if (!reinit) {
+			inode->i_op = &vboxsf_dir_iops;
+			inode->i_fop = &vboxsf_dir_fops;
+			/*
+			 * XXX: this probably should be set to the number of entries
+			 * in the directory plus two (. ..)
+			 */
+			set_nlink(inode, 1);
+		} else if (!S_ISDIR(inode->i_mode))
+			return -ESTALE;
+		inode->i_mode = mode;
 	} else if (SHFL_IS_SYMLINK(attr->mode)) {
-		inode->i_mode = sbi->o.fmode_set ? sbi->o.fmode : mode;
-		inode->i_mode &= ~sbi->o.fmask;
-		inode->i_mode |= S_IFLNK;
-		inode->i_op = &vboxsf_lnk_iops;
-		set_nlink(inode, 1);
+		if (sbi->o.fmode_set)
+			mode = sbi->o.fmode;
+		mode &= ~sbi->o.fmask;
+		mode |= S_IFLNK;
+		if (!reinit) {
+			inode->i_op = &vboxsf_lnk_iops;
+			set_nlink(inode, 1);
+		} else if (!S_ISLNK(inode->i_mode))
+			return -ESTALE;
+		inode->i_mode = mode;
 	} else {
-		inode->i_mode = sbi->o.fmode_set ? sbi->o.fmode : mode;
-		inode->i_mode &= ~sbi->o.fmask;
-		inode->i_mode |= S_IFREG;
-		inode->i_op = &vboxsf_reg_iops;
-		inode->i_fop = &vboxsf_reg_fops;
-		set_nlink(inode, 1);
+		if (sbi->o.fmode_set)
+			mode = sbi->o.fmode;
+		mode &= ~sbi->o.fmask;
+		mode |= S_IFREG;
+		if (!reinit) {
+			inode->i_op = &vboxsf_reg_iops;
+			inode->i_fop = &vboxsf_reg_fops;
+			set_nlink(inode, 1);
+		} else if (!S_ISREG(inode->i_mode))
+			return -ESTALE;
+		inode->i_mode = mode;
 	}
 
 	inode->i_uid = sbi->o.uid;
@@ -116,6 +131,7 @@ void vboxsf_init_inode(struct vboxsf_sbi *sbi, struct inode *inode,
 				 info->change_time.ns_relative_to_unix_epoch);
 	inode->i_mtime = ns_to_timespec64(
 			   info->modification_time.ns_relative_to_unix_epoch);
+	return 0;
 }
 
 int vboxsf_create_at_dentry(struct dentry *dentry,
@@ -199,7 +215,9 @@ int vboxsf_inode_revalidate(struct dentry *dentry)
 
 	dentry->d_time = jiffies;
 	sf_i->force_restat = 0;
-	vboxsf_init_inode(sbi, inode, &info);
+	err = vboxsf_init_inode(sbi, inode, &info, true);
+	if (err)
+		return err;
 
 	/*
 	 * If the file was changed on the host side we need to invalidate the

fs/vboxsf/vfsmod.h

@@ -82,8 +82,8 @@ extern const struct dentry_operations vboxsf_dentry_ops;
 
 /* from utils.c */
 struct inode *vboxsf_new_inode(struct super_block *sb);
-void vboxsf_init_inode(struct vboxsf_sbi *sbi, struct inode *inode,
-		       const struct shfl_fsobjinfo *info);
+int vboxsf_init_inode(struct vboxsf_sbi *sbi, struct inode *inode,
+		       const struct shfl_fsobjinfo *info, bool reinit);
 int vboxsf_create_at_dentry(struct dentry *dentry,
 			    struct shfl_createparms *params);
 int vboxsf_stat(struct vboxsf_sbi *sbi, struct shfl_string *path,