Index: uspace/srv/fs/mfs/mfs_ops.c
===================================================================
--- uspace/srv/fs/mfs/mfs_ops.c	(revision 6d4d88322786762d3f20ed62340bc6e25b401641)
+++ uspace/srv/fs/mfs/mfs_ops.c	(revision df3caec54044190645f17dd3758c6f48eefbf7ca)
@@ -69,5 +69,6 @@
 static int mfs_instance_get(service_id_t service_id,
     struct mfs_instance **instance);
-
+static int mfs_check_sanity(struct mfs_sb_info *sbi);
+static bool is_power_of_two(uint32_t n);
 
 static hash_table_t open_nodes;
@@ -261,4 +262,8 @@
 
 	sbi->itable_off = 2 + sbi->ibmap_blocks + sbi->zbmap_blocks;
+	if ((rc = mfs_check_sanity(sbi)) != EOK) {
+		fprintf(stderr, "Filesystem corrupted, invalid superblock");
+		goto out_error;
+	}
 
 	rc = block_cache_init(service_id, sbi->block_size, 0, cmode);
@@ -1071,4 +1076,27 @@
 }
 
+/** Filesystem sanity check
+ *
+ * @param Pointer to the MFS superblock.
+ *
+ * @return EOK on success, ENOTSUP otherwise.
+ */
+static int
+mfs_check_sanity(struct mfs_sb_info *sbi)
+{
+	if (!is_power_of_two(sbi->block_size) ||
+	    sbi->block_size < MFS_MIN_BLOCKSIZE ||
+	    sbi->block_size > MFS_MAX_BLOCKSIZE)
+		return ENOTSUP;
+	else if (sbi->ibmap_blocks == 0 || sbi->zbmap_blocks == 0)
+		return ENOTSUP;
+	else if (sbi->ninodes == 0 || sbi->nzones == 0)
+		return ENOTSUP;
+	else if (sbi->firstdatazone == 0)
+		return ENOTSUP;
+
+	return EOK;
+}
+
 static int
 mfs_close(service_id_t service_id, fs_index_t index)
@@ -1091,4 +1119,19 @@
 
 	return mfs_node_put(fn);
+}
+
+/** Check if a given number is a power of two.
+ *
+ * @param n	The number to check.
+ *
+ * @return	true if it is a power of two, false otherwise.
+ */
+static bool
+is_power_of_two(uint32_t n)
+{
+	if (n == 0)
+		return false;
+
+	return (n & (n - 1)) == 0;
 }