Re: NULL dereference in rpcauth_lookup_credcache

[Trond Myklebust <trondmy@hammerspace.com>]

On Mon, 2018-11-12 at 18:01 -0500, bfields@fieldses.org wrote:
> On Mon, Nov 12, 2018 at 09:17:16PM +0000, Trond Myklebust wrote:
> > On Mon, 2018-11-12 at 13:24 -0500, bfields@fieldses.org wrote:
> > > On Mon, Nov 12, 2018 at 05:59:33PM +0000, Trond Myklebust wrote:
> > > > On Sat, 2018-11-10 at 16:49 -0500, Bruce Fields wrote:
> > > > > Looks like it's the fault of
> > > > > 
> > > > > 07d02a67b7faae "SUNRPC: Simplify lookup code"
> > > > 
> > > > I'm having trouble reproducing this bug. I've tried both cthon
> > > > and
> > > > xfstests in a loop, so far without success (both NFSv3 and
> > > > v4.1,
> > > > but
> > > > only sec=sys). Is there anything else you're doing that I might
> > > > try?
> > > > 
> > > > e.g. Are you running multiple workloads in parallel? Different
> > > > users?..
> > > 
> > > Nothing that interesting.  Currently it's connectathon over v4,
> > > v3,
> > > v4/krb5, v3/krb5, v4/krb5i, v4/krb5p, v4.1, v4.1/krb5, but just
> > > serially
> > > one after the other.  Then some pynfs tests (which bypass the
> > > client),
> > > then xfstests over v4.2/sys.  And also a few one-off locking
> > > tests of
> > > my
> > > own that probably aren't a factor here.
> > > 
> > > (Hah, I just realized I was mounting with vers=4 and assuming
> > > that
> > > meant
> > > 4.0, but actually it's changed over time depending on the
> > > defaults,
> > > so
> > > currently those "v4" runs are actually all 4.2.  Gah.)
> > 
> > Are you perhaps both using RPCSEC_GSS w/ integrity checking for
> > your
> > EXCHANGE_ID authentication? The client will attempt to use that by
> > default if rpc.gssd is running.
> 
> Yes, in addition to the krb5i mount I'd expect the sys/krb5/krb5p
> mounts
> are using krb5i for EXCHANGE_ID.
> 
> > I ask because I think the issue might be with RPCSEC_GSS,
> > specifically
> > with the RPCSEC_GSS context destroy code, hence the 2 patches that
> > I
> > just sent out.
> 
> Looks like my tests pass after applying those two patches.
> 

Cool! Thanks for testing.

Chuck, do you think the above might also explain your sighting of the
same Oops?

Cheers
  Trond

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com