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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:   Tue, 26 Jul 2022 17:34:55 +0000
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Hello Jan-

> 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, le=
n=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

Thanks for testing.

May I ask that you file these as three separate bugs here:

https://bugzilla.linux-nfs.org/


--
Chuck Lever