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Date:      Wed, 12 Nov 2003 14:28:31 -0400 (AST)
From:      "Marc G. Fournier" <scrappy@hub.org>
To:        freebsd-stable@FreeBSD.ORG
Subject:   Re: kernel panic on jailed sshd - 4.9-release
Message-ID:  <20031112142539.Y56037@ganymede.hub.org>
In-Reply-To: <200311121658.hACGwPVJ045423@lurza.secnetix.de>
References:  <200311121658.hACGwPVJ045423@lurza.secnetix.de>

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On Wed, 12 Nov 2003, Oliver Fromme wrote:

> Possibly a program which now triggers a NULLFS problem. For example, it
> might be that some program in 4.8 used standard read/write to access
> files, and it was changed to use mmap() in 4.9, which can be a problem
> with NULLFS.
>
> Of course I could be wrong.  Something else could have caused that
> particular crash.  But still it is a good idea not to use NULLFS if
> possible.  (Particularly in a jail environment if you don't have strict
> control over which programs get executed, such as a user shell box.)

I stop'd using NULLFS myself awhile back, since I too was getting
problems, but figured I was over-tempting fate by using UNIONFS *and*
NULLFS at the same time ...

But, if we can get a core dump from the system in question, at least we
can try and isolate where the issue is ... it might be something that a
simple 2 line patch can fix ...

> If a miracle happened and NULLFS got stable recently, then the
> mount_null(8) manpage should be fixed, because it states just the
> opposite.  ;-)

What I'd love to see is the man page changed so that the BUGS section
indicates in what circumstances NULL/UNIONFS are unstable ... document it
so that ppl don't have to go through trial-n-error each time ...



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