gpt: make its header check a tiny bit more strict

* libparted/labels/gpt.c (_header_is_valid): Declare a header
to be invalid if its AlternateLBA is the same as MyLBA.

2009-10-21  Jim Meyering  <meyering@redhat.com>

complete most of gpt-CRC-related rewrite
* libparted/labels/gpt.c (_read_header): Remove now-unused function.

diff --git a/libparted/labels/gpt.c b/libparted/labels/gpt.c
index 6010fee..cbaffa9 100644 (file)
--- a/libparted/labels/gpt.c
+++ b/libparted/labels/gpt.c
@@ -620,8 +620,13 @@ _header_is_valid (const PedDevice *dev, GuidPartitionTableHeader_t *gpt,
   if (PED_LE64_TO_CPU (gpt->MyLBA) != my_lba)
     return 0;
 
+  PedSector alt_lba = PED_LE64_TO_CPU (gpt->AlternateLBA);
   /* The backup table's AlternateLBA must be 1.  */
-  if (my_lba != 1 && PED_LE64_TO_CPU (gpt->AlternateLBA) != 1)
+  if (my_lba != 1 && alt_lba != 1)
+    return 0;
+
+  /* The alt_lba must never be the same as my_lba.  */
+  if (alt_lba == my_lba)
     return 0;
 
   origcrc = gpt->HeaderCRC32;