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Subject: Re: NULL dereference in rpcauth_lookup_credcache
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <9d36177854ba176f46e7a9842aa0368cc508b599.camel@hammerspace.com>
Date:   Mon, 12 Nov 2018 16:00:50 -0800
Cc:     "bfields@fieldses.org" <bfields@fieldses.org>,
        "schumakeranna@gmail.com" <schumakeranna@gmail.com>,
        "chucklever@gmail.com" <chucklever@gmail.com>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
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Message-Id: <8B4BB2AC-D94B-4B76-BFF2-460303C8FE9B@oracle.com>
References: <20181108214452.GH6090@fieldses.org> <04114B00-B5A8-4F8A-B052-A266AED7725D@gmail.com> <20181110214939.GA16755@fieldses.org> <c986450a2d19fa796078ed51b9d0fb8a79eda696.camel@hammerspace.com> <20181112182454.GE16755@fieldses.org> <2e62a77385b4e5d91e2ca9128313cf817c46a1ae.camel@hammerspace.com> <20181112230149.GF16755@fieldses.org> <9d36177854ba176f46e7a9842aa0368cc508b599.camel@hammerspace.com>
To:     Trond Myklebust <trondmy@hammerspace.com>
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk


> On Nov 12, 2018, at 3:57 PM, Trond Myklebust <trondmy@hammerspace.com> wro=
te:
>=20
>> 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
>>>>>>=20
>>>>>> 07d02a67b7faae "SUNRPC: Simplify lookup code"
>>>>>=20
>>>>> 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=3Dsys). Is there anything else you're doing that I might
>>>>> try?
>>>>>=20
>>>>> e.g. Are you running multiple workloads in parallel? Different
>>>>> users?..
>>>>=20
>>>> 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.
>>>>=20
>>>> (Hah, I just realized I was mounting with vers=3D4 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.)
>>>=20
>>> 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.
>>=20
>> Yes, in addition to the krb5i mount I'd expect the sys/krb5/krb5p
>> mounts
>> are using krb5i for EXCHANGE_ID.
>>=20
>>> 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.
>>=20
>> Looks like my tests pass after applying those two patches.
>>=20
>=20
> Cool! Thanks for testing.
>=20
> Chuck, do you think the above might also explain your sighting of the
> same Oops?

Could be, I don=E2=80=99t think I saw it until I started testing NFSv4.
I won=E2=80=99t be able to confirm that until next week.


> Cheers
>  Trond
>=20
> --=20
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@hammerspace.com
>=20
>=20