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Minimum size of GPT partition table header

From: rahul dev
Subject: Minimum size of GPT partition table header
Date: Thu, 20 Sep 2012 12:14:28 +0800 (SGT)


   There seems to be a bug in function _header_is_valid() in file gpt.c.

static int
_header_is_valid (PedDisk const *disk, GuidPartitionTableHeader_t *gpt,
                  PedSector my_lba)
  uint32_t crc, origcrc;
  PedDevice const *dev = disk->dev;

  if (PED_LE64_TO_CPU (gpt->Signature) != GPT_HEADER_SIGNATURE)
    return 0;
   * "While the GUID Partition Table Header's size may increase
   * in the future it cannot span more than one block on the
   * device."  EFI Specification, version 1.10,
  if (PED_LE32_TO_CPU (gpt->HeaderSize) < pth_get_size_static (dev)
      || PED_LE32_TO_CPU (gpt->HeaderSize) > dev->sector_size)
    return 0;

The check gpt->HeaderSize < pth_get_size_static seems to be incorrect.
I think minimum size of gpt header is 92 bytes. So, correct check should be
gtp->HeaderSize < 92.

As mentioned in the EFI spec that the header size may increase in future, 
pth_get_size_static() will also return the increased size. In that case, if we 
are running parted on a disk partitioned by old versions, the above check would 
fail. For older versions, gpt->HeaderSize is 92, whereas pth_get_size_static() 
will be > 92 for newer versions (where gpt hdr size has been increased).

Any thoughts ?


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