fs/ntfs3: Restore overflow checking for attr size in mi_enum_attr

Fixed comment.
Removed explicit initialization for INDEX_ROOT.
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3/index.c

@@ -994,7 +994,7 @@ struct INDEX_ROOT *indx_get_root(struct ntfs_index *indx, struct ntfs_inode *ni,
 	struct ATTR_LIST_ENTRY *le = NULL;
 	struct ATTRIB *a;
 	const struct INDEX_NAMES *in = &s_index_names[indx->type];
-	struct INDEX_ROOT *root = NULL;
+	struct INDEX_ROOT *root;
 
 	a = ni_find_attr(ni, NULL, &le, ATTR_ROOT, in->name, in->name_len, NULL,
 			 mi);
@@ -1007,7 +1007,8 @@ struct INDEX_ROOT *indx_get_root(struct ntfs_index *indx, struct ntfs_inode *ni,
 	root = resident_data_ex(a, sizeof(struct INDEX_ROOT));
 
 	/* length check */
-	if (root && offsetof(struct INDEX_ROOT, ihdr) + le32_to_cpu(root->ihdr.used) >
+	if (root &&
+	    offsetof(struct INDEX_ROOT, ihdr) + le32_to_cpu(root->ihdr.used) >
 		    le32_to_cpu(a->res.data_size)) {
 		return NULL;
 	}

fs/ntfs3/record.c

@@ -220,6 +220,11 @@ struct ATTRIB *mi_enum_attr(struct mft_inode *mi, struct ATTRIB *attr)
 			return NULL;
 		}
 
+		if (off + asize < off) {
+			/* Overflow check. */
+			return NULL;
+		}
+
 		attr = Add2Ptr(attr, asize);
 		off += asize;
 	}

fs/ntfs3/super.c

@@ -1187,7 +1187,7 @@ static int ntfs_fill_super(struct super_block *sb, struct fs_context *fc)
 
 	/*
 	 * Typical $AttrDef contains up to 20 entries.
-	 * Check for extremely large size.
+	 * Check for extremely large/small size.
 	 */
 	if (inode->i_size < sizeof(struct ATTR_DEF_ENTRY) ||
 	    inode->i_size > 100 * sizeof(struct ATTR_DEF_ENTRY)) {