Re: mount * 2 + umount + lookup = GEOM panic

On Fri, Aug 18, 2006 at 10:25:08PM +0200, Pawel Jakub Dawidek wrote:
> 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_at_ didn't agree on committing it, so next time, please
> CC him:)

Just to satisfy my curiosity:  Do you have references to a discussion
of the problem?  When such a simple script triggers an architectural
issue, the latter is definitely worth taking a glance at. :-)
Thanks!

-- 
Yar