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Subject: Re: [PATCH] nfsd: fix oops on mixed NFSv4/NFSv3 client access
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <20200805191011.GB14429@fieldses.org>
Date:   Wed, 5 Aug 2020 15:17:54 -0400
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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Message-Id: <C7E5BAD1-FB46-4A0D-9D3A-031E9C09002C@oracle.com>
References: <20200805191011.GB14429@fieldses.org>
To:     Bruce Fields <bfields@fieldses.org>
Sender: linux-nfs-owner@vger.kernel.org
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Hi Bruce-

> On Aug 5, 2020, at 3:10 PM, bfields@fieldses.org wrote:
>=20
> From: "J. Bruce Fields" <bfields@redhat.com>
>=20
> If an NFSv2/v3 client breaks an NFSv4 client's delegation, it will hit =
a
> NULL dereference in nfsd_breaker_owns_lease().
>=20
> Easily reproduceable with for example
>=20
> 	mount -overs=3D4.2 server:/export /mnt/
> 	sleep 1h </mnt/file &
> 	mount -overs=3D3 server:/export /mnt2/
> 	touch /mnt2/file
>=20
> Reported-by: Robert Dinse <nanook@eskimo.com>
> Fixes: 28df3d1539de50 ("nfsd: clients don't need to break their own =
delegations")

May I add

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=3D208807

And send this in the first NFSD v5.9 -rc pull request?


> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> ---
> fs/nfsd/nfs4state.c | 2 ++
> 1 file changed, 2 insertions(+)
>=20
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 9fc0a1b9e4dd..45f3832d70d4 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -4597,6 +4597,8 @@ static bool nfsd_breaker_owns_lease(struct =
file_lock *fl)
> 	if (!i_am_nfsd())
> 		return NULL;
> 	rqst =3D kthread_data(current);
> +	if (!rqst->rq_lease_breaker)
> +		return NULL;
> 	clp =3D *(rqst->rq_lease_breaker);
> 	return dl->dl_stid.sc_client =3D=3D clp;
> }
> --=20
> 2.26.2
>=20

--
Chuck Lever