mount * 2 + umount + lookup = GEOM panic

[Pawel Jakub Dawidek]

On Fri, Aug 18, 2006 at 03:14:57PM -0400, Kris Kennaway wrote:
> On Fri, Aug 18, 2006 at 10:46:57PM +0400, Yar Tikhiy wrote:
> > Hi all,
> > 
> > Here is a recipe how to panic CURRENT's GENERIC kernel from the
> > command line:
> > 
> > (enter single-user mode)
> > 
> > # mount -r /usr
> > # mount -r /usr
> > # umount /usr
> > # cat
> > [panic!]
> > 
> > As shown below, the panic happens in GEOM when /bin/sh searches
> > $PATH for cat(1).  The recipe works in 6-STABLE, too.  Is anybody
> > interested?  Thanks!
> 
> This has been reported a number of times before, apparently it's
> difficult to solve.

No, it's difficult to solve in a architectural clean way, but IMHO this
bug should be fixed. I've a fix for this (which allows for multiple
read-only mounts). It's hackish, but works.

Unfortunately phk@ didn't agree on committing it, so next time, please
CC him:)

-- 
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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