[2597] 2009-09-15 Vladimir Serbinenko <address@hidden>

[Vladimir Serbinenko]

Revision: 2597
          http://svn.sv.gnu.org/viewvc/?view=rev&root=grub&revision=2597
Author:   phcoder
Date:     2009-09-15 10:36:29 +0000 (Tue, 15 Sep 2009)
Log Message:
-----------
2009-09-15  Vladimir Serbinenko  <address@hidden>

        * partmap/pc.c (pc_partition_map_iterate): Detect and break loops.

Modified Paths:
--------------
    trunk/grub2/ChangeLog
    trunk/grub2/partmap/msdos.c

Modified: trunk/grub2/ChangeLog
===================================================================
--- trunk/grub2/ChangeLog       2009-09-14 19:57:45 UTC (rev 2596)
+++ trunk/grub2/ChangeLog       2009-09-15 10:36:29 UTC (rev 2597)
@@ -1,3 +1,7 @@
+2009-09-15  Vladimir Serbinenko  <address@hidden>
+
+       * partmap/pc.c (pc_partition_map_iterate): Detect and break loops.
+
 2009-09-14  Colin Watson  <address@hidden>
 
        * commands/test.c (get_fileinfo): Return immediately if

Modified: trunk/grub2/partmap/msdos.c
===================================================================
--- trunk/grub2/partmap/msdos.c 2009-09-14 19:57:45 UTC (rev 2596)
+++ trunk/grub2/partmap/msdos.c 2009-09-15 10:36:29 UTC (rev 2597)
@@ -97,6 +97,8 @@
   struct grub_msdos_partition_mbr mbr;
   struct grub_msdos_partition_disk_label label;
   struct grub_disk raw;
+  int labeln = 0;
+  grub_disk_addr_t lastaddr;
 
   /* Enforce raw disk access.  */
   raw = *disk;
@@ -117,6 +119,18 @@
       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 (labeln && lastaddr == p.offset)
+       return grub_error (GRUB_ERR_BAD_PART_TABLE, "loop detected");
+
+      labeln++;
+      if ((labeln & (labeln - 1)) == 0)
+       lastaddr = p.offset;
+
       /* 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");