[bug #38035] Off by one error in enumerating MSDOS partitions

[Andrey Borzenkov]

URL:
  <http://savannah.gnu.org/bugs/?38035>

                 Summary: Off by one error in enumerating MSDOS partitions
                 Project: GNU GRUB
            Submitted by: arvidjaar
            Submitted on: Mon 07 Jan 2013 02:24:39 PM GMT
                Category: Disk &amp; Partition
                Severity: Major
                Priority: 5 - Normal
              Item Group: Software Error
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 
                 Release: Bazaar - trunk
         Reproducibility: Every Time
         Planned Release: None

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Details:

As reported in https://bugzilla.novell.com/show_bug.cgi?id=779534#c19 under
some conditions GRUB2 includes extended partition in total partition numbering
causing wrong numbers to be assigned. This happens under following conditions

- extended primary partition exists
- the very first next extended boot record has extended partition as the first
entry (usually first entry points to normal partition)

Depending on number of primary partitions, it could also possibly happen for
next EBR as well.

Full partitions dump is available as
https://bugzilla.novell.com/attachment.cgi?id=519076

The reason is off by one error in grub_partition_msdos_iterate(). p.number
starts counting partitions with 0, so primary partitions have number 0..3 and
at the point p.number is incremented it still points to *previous* partition.
So it should be p.number < 3 to apply to primary partitions only.

Patch against trunk attached. It is confirmed as working by original reporter.



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File Attachments:


-------------------------------------------------------
Date: Mon 07 Jan 2013 02:24:39 PM GMT  Name:
grub2-fix-enumeration-of-extended-partition.patch  Size: 2kB   By: arvidjaar

<http://savannah.gnu.org/bugs/download.php?file_id=27215>

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