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NFSD: Support write delegations in LAYOUTGET

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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.

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.

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.

To permit LAYOUT* operations in this case, add OWNER_OVERRIDE when
checking the access permission of the incoming file handle for
LAYOUTGET and LAYOUTCOMMIT.

Cc: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org # v6.6+
Message-Id: 4E9C0D74-A06D-4DC3-A48A-73034DC40395@oracle.com
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Chuck Lever 2024-06-11 15:36:46 -04:00
parent e5d85ec52b
commit abc02e5602
1 changed files with 3 additions and 2 deletions
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5
fs/nfsd/nfs4proc.c
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@ -2269,7 +2269,7 @@ nfsd4_layoutget(struct svc_rqst *rqstp,
const struct nfsd4_layout_ops *ops;
struct nfs4_layout_stateid *ls;
__be32 nfserr;
int accmode = NFSD_MAY_READ_IF_EXEC;
int accmode = NFSD_MAY_READ_IF_EXEC | NFSD_MAY_OWNER_OVERRIDE;
switch (lgp->lg_seg.iomode) {
case IOMODE_READ:
@ -2359,7 +2359,8 @@ nfsd4_layoutcommit(struct svc_rqst *rqstp,
struct nfs4_layout_stateid *ls;
__be32 nfserr;
nfserr = fh_verify(rqstp, current_fh, 0, NFSD_MAY_WRITE);
nfserr = fh_verify(rqstp, current_fh, 0,
NFSD_MAY_WRITE | NFSD_MAY_OWNER_OVERRIDE);
if (nfserr)
goto out;