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Date:      Tue, 11 Apr 2017 17:29:47 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-bugs@FreeBSD.org
Subject:   [Bug 218568] vdev_geom_attach_by_guids can attach to wrong partition
Message-ID:  <bug-218568-8@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D218568

            Bug ID: 218568
           Summary: vdev_geom_attach_by_guids can attach to wrong
                    partition
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs@FreeBSD.org
          Reporter: asomers@FreeBSD.org

When opening a vdev whose path is unknown, vdev_geom must find a geom provi=
der
with a label whose guids match te desired vdev.  However, due to partitioni=
ng,
it is possible that two non-synonomous providers will share two labels.  For
example, if the first partition starts at the beginning of the drive, then =
ada0
and ada0p1 will share the first label.  More troubling, if the last partiti=
on
runs to the end of the drive, then ada0p3 and ada0 will share the last labe=
l.=20
If vdev_geom opens ada0 when it should've opened ada0p3, then the pool won'=
t be
readable.  If it opens ada0 when it should've opened ada0p1, then it will
corrupt some other partition when it writes the 3rd and 4th labels.

The easiest way to observe this problem is to install ZFS to a pair of mirr=
ored
drives, using the default GPT partitioning scheme.  Power off, swap the dri=
ves,
and power back on.  Depending on the order that geom probes its providers, =
ZFS
may or may not attach to the correct partitions.  If it doesn't, then impor=
ting
the pool will fail somewhere up stack, and the system will be left at the
mountroot> prompt.

--=20
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