libfdisk: (gpt) fix check for beginning of protective partition

Search for the protective partition before attempting to validate that
it covers the GPT header. Some hybrid MBRs list partitions out of order.
For example, CoreOS images ship with a hybrid MBR that lists the boot
partition first and the protective partition second in order to maintain
compatibility with old versions of Xen's PV-GRUB.

Signed-off-by: Michael Marineau <michael.marineau@coreos.com>

diff --git a/libfdisk/src/gpt.c b/libfdisk/src/gpt.c
index a7766da60478c9f4bb5dc9c7a13ea62b79f25c98..989fd752c52647f85dce59bce5aca8abead38ca6 100644 (file)
--- a/libfdisk/src/gpt.c
+++ b/libfdisk/src/gpt.c
@@ -678,11 +678,6 @@ static int valid_pmbr(struct fdisk_context *cxt)
        if (le16_to_cpu(pmbr->signature) != MSDOS_MBR_SIGNATURE)
                goto done;
 
-       /* LBA of the GPT partition header */
-       if (pmbr->partition_record[0].starting_lba !=
-           cpu_to_le32(GPT_PRIMARY_PARTITION_TABLE_LBA))
-               goto done;
-
        /* seems like a valid MBR was found, check DOS primary partitions */
        for (i = 0; i < 4; i++) {
                if (pmbr->partition_record[i].os_type == EFI_PMBR_OSTYPE) {
@@ -693,13 +688,18 @@ static int valid_pmbr(struct fdisk_context *cxt)
                         */
                        part = i;
                        ret = GPT_MBR_PROTECTIVE;
-                       goto check_hybrid;
+                       break;
                }
        }
 
        if (ret != GPT_MBR_PROTECTIVE)
                goto done;
-check_hybrid:
+
+       /* LBA of the GPT partition header */
+       if (pmbr->partition_record[part].starting_lba !=
+           cpu_to_le32(GPT_PRIMARY_PARTITION_TABLE_LBA))
+               goto done;
+
        for (i = 0 ; i < 4; i++) {
                if ((pmbr->partition_record[i].os_type != EFI_PMBR_OSTYPE) &&
                    (pmbr->partition_record[i].os_type != 0x00))