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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Jan Kasiak <j.kasiak@gmail.com>
CC:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: NLM 4 Infinite Loop Bug
Thread-Topic: NLM 4 Infinite Loop Bug
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Date:   Wed, 27 Jul 2022 17:21:22 +0000
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> On Jul 27, 2022, at 1:20 PM, Jan Kasiak <j.kasiak@gmail.com> wrote:
>=20
> Hi Chuck,
>=20
> I created 3 bugs:
>=20
> https://bugzilla.linux-nfs.org/show_bug.cgi?id=3D390
> For the original issue I reported with FREE_ALL
> because I'm not sure if its fully fixed.
>=20
> https://bugzilla.linux-nfs.org/show_bug.cgi?id=3D391
> For scenario A
>=20
> https://bugzilla.linux-nfs.org/show_bug.cgi?id=3D392
> For scenario B/C because they are very similar

Thanks. Jeff and I will have a look at these soon.


> Thanks,
> -Jan
>=20
> On Tue, Jul 26, 2022 at 1:34 PM Chuck Lever III <chuck.lever@oracle.com> =
wrote:
>>=20
>> Hello Jan-
>>=20
>>> On Jul 26, 2022, at 1:16 PM, Jan Kasiak <j.kasiak@gmail.com> wrote:
>>>=20
>>> Hi all,
>>>=20
>>> Even after applying the above two patches, I have discovered a new set
>>> of NLM 4 requests that break lockd.
>>>=20
>>> Unfortunately, I don't have enough experience to suggest a fix, but
>>> would be glad to test anyone's attempt.
>>>=20
>>> All requests are non-blocking.
>>>=20
>>> Scenario A
>>> =3D=3D=3D=3D=3D=3D=3D=3D=3D
>>> lock(offset=3DUINT64_MAX, len=3D100) - GRANTED
>>> free_all() - never finishes and lockd thread is stuck busy looping
>>>=20
>>> Scenario B
>>> =3D=3D=3D=3D=3D=3D=3D=3D
>>> lock(svid=3D1, offset=3DUINT64_MAX, len=3D100) - GRANTED
>>>=20
>>> test(svid=3D2, offset=3DUINT64_MAX, len=3D50) - DENIED
>>> correct, holder offset, len are (UINT64_MAX, 100)
>>>=20
>>> test(svid=3D2, offset=3D75, len=3D10) - DENIED
>>> wrong, because holder (offset, len) are wrong (UINT64_MAX, 100),
>>> because the above
>>> lock overflows during comparison to (49, 50)
>>>=20
>>> Scenario C
>>> =3D=3D=3D=3D=3D=3D=3D=3D
>>> lock(svid=3D1, offset=3DUINT64_MAX, len=3D100) - GRANTED
>>>=20
>>> test(svid=3D2, offset=3DUINT64_MAX, len=3D50) - DENIED
>>> correct, holder offset, len are (UINT64_MAX, 100)
>>>=20
>>> unlock(svid=3D1, offset=3DUINT64_MAX, len=3D50) - GRANTED
>>> weird, because it has now created a lock at (offset=3DUINT64_MAX + 50, =
len=3D50)
>>> not sure what the correct behavior should be here - FBIG error?
>>>=20
>>> test(svid=3D2, offset=3D75, len=3D10) - DENIED
>>> wrong, because holder offset, len are wrong (49, 50), because the above
>>> unlock has overflowed the offset
>>=20
>> Thanks for testing.
>>=20
>> May I ask that you file these as three separate bugs here:
>>=20
>> https://bugzilla.linux-nfs.org/
>>=20
>>=20
>>=20
>> --
>> Chuck Lever
>>=20
>>=20
>>=20

--
Chuck Lever