8.0-RC1: kernel page fault in NLM master thread (VIMAGE or ZFS
jamie at FreeBSD.org
Wed Oct 7 20:08:47 UTC 2009
Rick Macklem wrote:
> On Sun, 27 Sep 2009, Robert Watson wrote:
>> On Fri, 25 Sep 2009, Jamie Gritton wrote:
>>> It seems to be NFS related. I think the null pointer in question is
>>> from the export's anonymous credential. Try the patch below and see
>>> if it helps (which I guess means run it overnight and see if it
>>> crashes again). I've also patched a similar missing cred prison in
>>> GSS_SVC, since I'm not versed enough in NFS/RPC stuff to know if it
>>> might be the problem.
>> This is one of the reasons I really dislike "magic" credentials and
>> special handling of NULL credentials -- they always get into code the
>> author doesn't expect, and either there are bad pointer dereferences,
>> or incorrect security decisions. It's almost always the case that a
>> correct credential should have been cached or generated at some
>> earlier point to represent the security context...
> I don't really understand prisons/jails, but would creating these
> credentials via:
> crdup(td->td_ucred); // duplicating the daemon thread's cred
> - and then replacing the <uid,gids>
> make sense as an alternative to starting with crget()?
> (ie. All the other stuff except <uid,gids> would be "inherited" from the
> credential for the daemon thread.)
That sounds right to me for cases when the cred is based on passed
UID/GIDs. Perhaps you'd want to use the UID-changing helper functions on
kern_prot.c, or perhaps a new helper or helpers just for the circumstance.
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