sanitize ecryptfs ->mount()

kill ecryptfs_read_super(), reorder code allowing to use
normal d_alloc_root() instead of opencoding it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ecryptfs/inode.c

@@ -441,7 +441,6 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
 	struct qstr lower_name;
 	int rc = 0;
 
-	d_set_d_op(ecryptfs_dentry, &ecryptfs_dops);
 	if ((ecryptfs_dentry->d_name.len == 1
 	     && !strcmp(ecryptfs_dentry->d_name.name, "."))
 	    || (ecryptfs_dentry->d_name.len == 2

fs/ecryptfs/main.c

@@ -141,21 +141,9 @@ int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry)
 	return rc;
 }
 
-/**
- * ecryptfs_interpose
- * @lower_dentry: Existing dentry in the lower filesystem
- * @dentry: ecryptfs' dentry
- * @sb: ecryptfs's super_block
- * @flags: flags to govern behavior of interpose procedure
- *
- * Interposes upper and lower dentries.
- *
- * Returns zero on success; non-zero otherwise
- */
-int ecryptfs_interpose(struct dentry *lower_dentry, struct dentry *dentry,
-		       struct super_block *sb, u32 flags)
+static inode *ecryptfs_get_inode(struct inode *lower_inode,
+		       struct super_block *sb)
 {
-	struct inode *lower_inode;
 	struct inode *inode;
 	int rc = 0;
 
@@ -189,17 +177,38 @@ int ecryptfs_interpose(struct dentry *lower_dentry, struct dentry *dentry,
 	if (special_file(lower_inode->i_mode))
 		init_special_inode(inode, lower_inode->i_mode,
 				   lower_inode->i_rdev);
-	d_set_d_op(dentry, &ecryptfs_dops);
 	fsstack_copy_attr_all(inode, lower_inode);
 	/* This size will be overwritten for real files w/ headers and
 	 * other metadata */
 	fsstack_copy_inode_size(inode, lower_inode);
+	return inode;
+out:
+	return ERR_PTR(rc);
+}
+
+/**
+ * ecryptfs_interpose
+ * @lower_dentry: Existing dentry in the lower filesystem
+ * @dentry: ecryptfs' dentry
+ * @sb: ecryptfs's super_block
+ * @flags: flags to govern behavior of interpose procedure
+ *
+ * Interposes upper and lower dentries.
+ *
+ * Returns zero on success; non-zero otherwise
+ */
+int ecryptfs_interpose(struct dentry *lower_dentry, struct dentry *dentry,
+		       struct super_block *sb, u32 flags)
+{
+	struct inode *lower_inode = lower_dentry->d_inode;
+	struct inode *inode = ecryptfs_get_inode(lower_inode, sb);
+	if (IS_ERR(inode)
+		return PTR_ERR(inode);
 	if (flags & ECRYPTFS_INTERPOSE_FLAG_D_ADD)
 		d_add(dentry, inode);
 	else
 		d_instantiate(dentry, inode);
-out:
-	return rc;
+	return 0;
 }
 
 enum { ecryptfs_opt_sig, ecryptfs_opt_ecryptfs_sig,
@@ -491,60 +500,12 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options)
 struct kmem_cache *ecryptfs_sb_info_cache;
 static struct file_system_type ecryptfs_fs_type;
 
-/**
- * ecryptfs_read_super
- * @sb: The ecryptfs super block
- * @dev_name: The path to mount over
- *
- * Read the super block of the lower filesystem, and use
- * ecryptfs_interpose to create our initial inode and super block
- * struct.
- */
-static int ecryptfs_read_super(struct super_block *sb, const char *dev_name)
-{
-	struct path path;
-	int rc;
-
-	rc = kern_path(dev_name, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
-	if (rc) {
-		ecryptfs_printk(KERN_WARNING, "path_lookup() failed\n");
-		goto out;
-	}
-	if (path.dentry->d_sb->s_type == &ecryptfs_fs_type) {
-		rc = -EINVAL;
-		printk(KERN_ERR "Mount on filesystem of type "
-			"eCryptfs explicitly disallowed due to "
-			"known incompatibilities\n");
-		goto out_free;
-	}
-	ecryptfs_set_superblock_lower(sb, path.dentry->d_sb);
-	sb->s_maxbytes = path.dentry->d_sb->s_maxbytes;
-	sb->s_blocksize = path.dentry->d_sb->s_blocksize;
-	ecryptfs_set_dentry_lower(sb->s_root, path.dentry);
-	ecryptfs_set_dentry_lower_mnt(sb->s_root, path.mnt);
-	rc = ecryptfs_interpose(path.dentry, sb->s_root, sb, 0);
-	if (rc)
-		goto out_free;
-	rc = 0;
-	goto out;
-out_free:
-	path_put(&path);
-out:
-	return rc;
-}
-
 /**
  * ecryptfs_get_sb
  * @fs_type
  * @flags
  * @dev_name: The path to mount over
  * @raw_data: The options passed into the kernel
- *
- * The whole ecryptfs_get_sb process is broken into 3 functions:
- * ecryptfs_parse_options(): handle options passed to ecryptfs, if any
- * ecryptfs_read_super(): this accesses the lower filesystem and uses
- *                        ecryptfs_interpose to perform most of the linking
- * ecryptfs_interpose(): links the lower filesystem into ecryptfs (inode.c)
  */
 static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags,
 			const char *dev_name, void *raw_data)
@@ -553,6 +514,8 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
 	struct ecryptfs_sb_info *sbi;
 	struct ecryptfs_dentry_info *root_info;
 	const char *err = "Getting sb failed";
+	struct inode *inode;
+	struct path path;
 	int rc;
 
 	sbi = kmem_cache_zalloc(ecryptfs_sb_info_cache, GFP_KERNEL);
@@ -575,10 +538,8 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
 
 	s->s_flags = flags;
 	rc = bdi_setup_and_register(&sbi->bdi, "ecryptfs", BDI_CAP_MAP_COPY);
-	if (rc) {
-		deactivate_locked_super(s);
-		goto out;
-	}
+	if (rc)
+		goto out1;
 
 	ecryptfs_set_superblock_private(s, sbi);
 	s->s_bdi = &sbi->bdi;
@@ -586,34 +547,54 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
 	/* ->kill_sb() will take care of sbi after that point */
 	sbi = NULL;
 	s->s_op = &ecryptfs_sops;
+	s->s_d_op = &ecryptfs_dops;
 
-	rc = -ENOMEM;
-	s->s_root = d_alloc(NULL, &(const struct qstr) {
-			     .hash = 0,.name = "/",.len = 1});
+	err = "Reading sb failed";
+	rc = kern_path(dev_name, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
+	if (rc) {
+		ecryptfs_printk(KERN_WARNING, "kern_path() failed\n");
+		goto out1;
+	}
+	if (path.dentry->d_sb->s_type == &ecryptfs_fs_type) {
+		rc = -EINVAL;
+		printk(KERN_ERR "Mount on filesystem of type "
+			"eCryptfs explicitly disallowed due to "
+			"known incompatibilities\n");
+		goto out_free;
+	}
+	ecryptfs_set_superblock_lower(s, path.dentry->d_sb);
+	s->s_maxbytes = path.dentry->d_sb->s_maxbytes;
+	s->s_blocksize = path.dentry->d_sb->s_blocksize;
+
+	inode = ecryptfs_get_inode(path.dentry->d_inode, s);
+	rc = PTR_ERR(inode);
+	if (IS_ERR(inode))
+		goto out_free;
+
+	s->s_root = d_alloc_root(inode);
 	if (!s->s_root) {
-		deactivate_locked_super(s);
-		goto out;
+		iput(inode);
+		rc = -ENOMEM;
+		goto out_free;
 	}
-	d_set_d_op(s->s_root, &ecryptfs_dops);
-	s->s_root->d_sb = s;
-	s->s_root->d_parent = s->s_root;
 
+	rc = -ENOMEM;
 	root_info = kmem_cache_zalloc(ecryptfs_dentry_info_cache, GFP_KERNEL);
-	if (!root_info) {
-		deactivate_locked_super(s);
-		goto out;
-	}
+	if (!root_info)
+		goto out_free;
+
 	/* ->kill_sb() will take care of root_info */
 	ecryptfs_set_dentry_private(s->s_root, root_info);
+	ecryptfs_set_dentry_lower(s->s_root, path.dentry);
+	ecryptfs_set_dentry_lower_mnt(s->s_root, path.mnt);
+
 	s->s_flags |= MS_ACTIVE;
-	rc = ecryptfs_read_super(s, dev_name);
-	if (rc) {
-		deactivate_locked_super(s);
-		err = "Reading sb failed";
-		goto out;
-	}
 	return dget(s->s_root);
 
+out_free:
+	path_put(&path);
+out1:
+	deactivate_locked_super(s);
 out:
 	if (sbi) {
 		ecryptfs_destroy_mount_crypt_stat(&sbi->mount_crypt_stat);