nfsd: take struct file setup fully into nfs4_preprocess_stateid_op

This patch changes nfs4_preprocess_stateid_op so it always returns
a valid struct file if it has been asked for that.  For that we
now allocate a temporary struct file for special stateids, and check
permissions if we got the file structure from the stateid.  This
ensures that all callers will get their handling of special stateids
right, and avoids code duplication.

There is a little wart in here because the read code needs to know
if we allocated a file structure so that it can copy around the
read-ahead parameters.  In the long run we should probably aim to
cache full file structures used with special stateids instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 49 insertions, 11 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index f8d5081..61dfb33 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4576,6 +4576,9 @@ nfsd4_lookup_stateid(struct nfsd4_compound_state *cstate,
 static struct file *
 nfs4_find_file(struct nfs4_stid *s, int flags)
 {
+	if (!s)
+		return NULL;
+
 	switch (s->sc_type) {
 	case NFS4_DELEG_STID:
 		if (WARN_ON_ONCE(!s->sc_file->fi_deleg_file))
@@ -4607,27 +4610,63 @@ nfs4_check_olstateid(struct svc_fh *fhp, struct nfs4_ol_stateid *ols, int flags)
 	return nfs4_check_openmode(ols, flags);
 }
 
+static __be32
+nfs4_check_file(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfs4_stid *s,
+		struct file **filpp, bool *tmp_file, int flags)
+{
+	int acc = (flags & RD_STATE) ? NFSD_MAY_READ : NFSD_MAY_WRITE;
+	struct file *file;
+	__be32 status;
+
+	file = nfs4_find_file(s, flags);
+	if (file) {
+		status = nfsd_permission(rqstp, fhp->fh_export, fhp->fh_dentry,
+				acc | NFSD_MAY_OWNER_OVERRIDE);
+		if (status) {
+			fput(file);
+			return status;
+		}
+
+		*filpp = file;
+	} else {
+		status = nfsd_open(rqstp, fhp, S_IFREG, acc, filpp);
+		if (status)
+			return status;
+
+		if (tmp_file)
+			*tmp_file = true;
+	}
+
+	return 0;
+}
+
 /*
  * Checks for stateid operations
  */
 __be32
-nfs4_preprocess_stateid_op(struct net *net, struct nfsd4_compound_state *cstate,
-			   stateid_t *stateid, int flags, struct file **filpp)
+nfs4_preprocess_stateid_op(struct svc_rqst *rqstp,
+		struct nfsd4_compound_state *cstate, stateid_t *stateid,
+		int flags, struct file **filpp, bool *tmp_file)
 {
 	struct svc_fh *fhp = &cstate->current_fh;
 	struct inode *ino = d_inode(fhp->fh_dentry);
+	struct net *net = SVC_NET(rqstp);
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-	struct nfs4_stid *s;
+	struct nfs4_stid *s = NULL;
 	__be32 status;
 
 	if (filpp)
 		*filpp = NULL;
+	if (tmp_file)
+		*tmp_file = false;
 
 	if (grace_disallows_io(net, ino))
 		return nfserr_grace;
 
-	if (ZERO_STATEID(stateid) || ONE_STATEID(stateid))
-		return check_special_stateids(net, fhp, stateid, flags);
+	if (ZERO_STATEID(stateid) || ONE_STATEID(stateid)) {
+		status = check_special_stateids(net, fhp, stateid, flags);
+		goto done;
+	}
 
 	status = nfsd4_lookup_stateid(cstate, stateid,
 				NFS4_DELEG_STID|NFS4_OPEN_STID|NFS4_LOCK_STID,
@@ -4652,13 +4691,12 @@ nfs4_preprocess_stateid_op(struct net *net, struct nfsd4_compound_state *cstate,
 		break;
 	}
 
-	if (!status && filpp) {
-		*filpp = nfs4_find_file(s, flags);
-		if (!*filpp)
-			status = nfserr_serverfault;
-	}
+done:
+	if (!status && filpp)
+		status = nfs4_check_file(rqstp, fhp, s, filpp, tmp_file, flags);
 out:
-	nfs4_put_stid(s);
+	if (s)
+		nfs4_put_stid(s);
 	return status;
 }