diff --git a/ChangeLog b/ChangeLog
index 752bde8..eac8b8a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2009-07-25  Vladimir Serbinenko  <address@hidden>
+
+	* partmap/pc.c (pc_partition_map_iterate): Detect and break loops.
+
 2009-07-25  Felix Zielcke  <address@hidden>
 
 	* kern/file.c (grub_file_open): Revert to previous check with
diff --git a/partmap/pc.c b/partmap/pc.c
index 6f68ecf..e64f118 100644
--- a/partmap/pc.c
+++ b/partmap/pc.c
@@ -97,6 +97,9 @@ pc_partition_map_iterate (grub_disk_t disk,
   struct grub_pc_partition_mbr mbr;
   struct grub_pc_partition_disk_label label;
   struct grub_disk raw;
+  int labeln = 1, lastlabeln = 1;
+  /* Just not zero. It will be overwritten during first iteration. */
+  grub_disk_addr_t lastaddr = 0x1;
 
   /* Enforce raw disk access.  */
   raw = *disk;
@@ -117,6 +120,21 @@ pc_partition_map_iterate (grub_disk_t disk,
       if (grub_disk_read (&raw, p.offset, 0, sizeof (mbr), &mbr))
 	goto finish;
 
+      /* This is our loop-detection algorithm. It works the following way:
+	 It saves last position which was a power of two. Then it compares the
+	 saved value with a current one. This way it's guaranteed that the loop
+	 will be broken by at most third walk.
+       */
+      if (lastaddr == p.offset)
+	return grub_error (GRUB_ERR_BAD_PART_TABLE, "loop detected");
+
+      labeln++;
+      if (labeln == (lastlabeln << 1))
+	{
+	  lastaddr = p.offset;
+	  lastlabeln <<= 1;
+	}
+
       /* Check if it is valid.  */
       if (mbr.signature != grub_cpu_to_le16 (GRUB_PC_PARTITION_SIGNATURE))
 	return grub_error (GRUB_ERR_BAD_PART_TABLE, "no signature");