[PATCH v2 5/5] NFSD: Don't apply NFS version-specific behavior to LOCALIO requests

[Chuck Lever <cel@kernel.org>]

LOCALIO serves NFS clients of every version through one entry point,
so no protocol version is associated with such a request.
nfsd_set_fh_dentry() selects version-specific behavior anyway: its
switch keys off fh_maxsize, and nfsd_open_local_fh() passes
NFS4_FHSIZE because that is the size of the buffer it copies into, so
LOCALIO lands in the NFSv4 arm. fh_getattr() keys off fh_maxsize too
and does run on a LOCALIO open, adding STATX_BTIME and
STATX_CHANGE_COOKIE to the mask it requests: work on filesystems that
compute them for a caller that never reads them.

nfsd_open_local_fh() only verifies a handle it received, so it has no
maximum size to state. Pass NFSD_FHSIZE_UNSPEC as nlm_fopen() already
does, which selects the switch arm that applies no version-specific
behavior, and state the bound on the copy out of struct nfs_fh as
NFS_MAXFHSIZE.

Suggested-by: NeilBrown <neil@brown.name>
Signed-off-by: Chuck Lever <cel@kernel.org>
---
 fs/nfsd/localio.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/localio.c b/fs/nfsd/localio.c
index 4110be02b750..33b56d1b3f44 100644
--- a/fs/nfsd/localio.c
+++ b/fs/nfsd/localio.c
@@ -11,7 +11,6 @@
 #include <linux/exportfs.h>
 #include <linux/sunrpc/svcauth.h>
 #include <linux/sunrpc/clnt.h>
-#include <linux/nfs4.h>
 #include <linux/nfs_common.h>
 #include <linux/nfs_fh.h>
 #include <linux/nfslocalio.h>
@@ -54,7 +53,7 @@ nfsd_open_local_fh(struct net *net, struct auth_domain *dom,
 	struct nfsd_file *localio;
 	__be32 beres;
 
-	if (nfs_fh->size > NFS4_FHSIZE)
+	if (nfs_fh->size > NFS_MAXFHSIZE)
 		return ERR_PTR(-EINVAL);
 
 	if (!nfsd_net_try_get(net))
@@ -67,7 +66,7 @@ nfsd_open_local_fh(struct net *net, struct auth_domain *dom,
 		return localio;
 
 	/* nfs_fh -> svc_fh */
-	fh_init(&fh, NFS4_FHSIZE);
+	fh_init(&fh, NFSD_FHSIZE_UNSPEC);
 	fh.fh_handle.fh_size = nfs_fh->size;
 	memcpy(fh.fh_handle.fh_raw, nfs_fh->data, nfs_fh->size);
 
-- 
2.54.0