https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=218568
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: asom...@freebsd.org
When opening a vdev whose path is unknown, vdev_geom must find a geom provider
with a label whose guids match te desired vdev. However, due to partitioning,
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 partition
runs to the end of the drive, then ada0p3 and ada0 will share the last label.
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 mirrored
drives, using the default GPT partitioning scheme. Power off, swap the drives,
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 importing
the pool will fail somewhere up stack, and the system will be left at the
mountroot> prompt.
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