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Message-ID: <98ef88e17f3996c2584f49be34bbee0ec78d72b1.camel@kernel.org>
Subject: Re: [PATCH v2] NFSD: Support write delegations in LAYOUTGET
From: Jeff Layton <jlayton@kernel.org>
To: cel@kernel.org, linux-nfs@vger.kernel.org
Cc: Neil Brown <neilb@suse.de>, Dai Ngo <dai.ngo@oracle.com>, Olga
 Kornievskaia <kolga@netapp.com>, Tom Talpey <tom@talpey.com>, Chuck Lever
 <chuck.lever@oracle.com>, Christoph Hellwig <hch@lst.de>
Date: Wed, 12 Jun 2024 09:52:01 -0400
In-Reply-To: <20240611193645.65792-2-cel@kernel.org>
References: <20240611193645.65792-2-cel@kernel.org>
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On Tue, 2024-06-11 at 15:36 -0400, cel@kernel.org wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
>=20
> I noticed LAYOUTGET(LAYOUTIOMODE4_RW) returning NFS4ERR_ACCESS
> unexpectedly. The NFS client had created a file with mode 0444, and
> the server had returned a write delegation on the OPEN(CREATE). The
> client was requesting a RW layout using the write delegation stateid
> so that it could flush file modifications.
>=20
> Creating a read-only file does not seem to be problematic for
> NFSv4.1 without pNFS, so I began looking at NFSD's implementation of
> LAYOUTGET.
>=20
> The failure was because fh_verify() was doing a permission check as
> part of verifying the FH presented during the LAYOUTGET. It uses the
> loga_iomode value to specify the @accmode argument to fh_verify().
> fh_verify(MAY_WRITE) on a file whose mode is 0444 fails with -EACCES.
>=20
> To permit LAYOUT* operations in this case, add OWNER_OVERRIDE when
> checking the access permission of the incoming file handle for
> LAYOUTGET and LAYOUTCOMMIT.
>=20
> Cc: Christoph Hellwig <hch@lst.de>
> X-Cc: stable@vger.kernel.org=C2=A0# v6.6+
> Message-Id: 4E9C0D74-A06D-4DC3-A48A-73034DC40395@oracle.com
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
> =C2=A0fs/nfsd/nfs4proc.c | 5 +++--
> =C2=A01 file changed, 3 insertions(+), 2 deletions(-)
>=20
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 46bd20fe5c0f..2e39cf2e502a 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -2269,7 +2269,7 @@ nfsd4_layoutget(struct svc_rqst *rqstp,
> =C2=A0	const struct nfsd4_layout_ops *ops;
> =C2=A0	struct nfs4_layout_stateid *ls;
> =C2=A0	__be32 nfserr;
> -	int accmode =3D NFSD_MAY_READ_IF_EXEC;
> +	int accmode =3D NFSD_MAY_READ_IF_EXEC |
> NFSD_MAY_OWNER_OVERRIDE;
> =C2=A0
> =C2=A0	switch (lgp->lg_seg.iomode) {
> =C2=A0	case IOMODE_READ:
> @@ -2359,7 +2359,8 @@ nfsd4_layoutcommit(struct svc_rqst *rqstp,
> =C2=A0	struct nfs4_layout_stateid *ls;
> =C2=A0	__be32 nfserr;
> =C2=A0
> -	nfserr =3D fh_verify(rqstp, current_fh, 0, NFSD_MAY_WRITE);
> +	nfserr =3D fh_verify(rqstp, current_fh, 0,
> +			=C2=A0=C2=A0 NFSD_MAY_WRITE |
> NFSD_MAY_OWNER_OVERRIDE);
> =C2=A0	if (nfserr)
> =C2=A0		goto out;
> =C2=A0

Reviewed-by: Jeff Layton <jlayton@kernel.org>