bin/52828: makefs UFS2 lazy inode initialization is buggy

[markj%FreeBSD.org@localhost]

>Number:         52828
>Category:       bin
>Synopsis:       makefs UFS2 lazy inode initialization is buggy
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Dec 16 20:55:00 +0000 2017
>Originator:     Mark Johnston
>Release:        
>Organization:
>Environment:
>Description:
makefs(8) emulates UFS2 in performing lazy initialization of inode blocks when allocating and writing inodes. However, it only ever initializes one inode block at a time, which may be insufficient. If so, a later initialization may clobber an inode, resulting in an inconsistent filesystem.
>How-To-Repeat:
Not sure. I hit the issue while building VM images from a FreeBSD src tree. I hit a panic in FFS, and later discovered that makefs was generating filesystems containing inconsistencies (according to fsck_ffs).
>Fix:
I committed a minimal fix for the problem to FreeBSD: https://svnweb.freebsd.org/changeset/base/326912