[PATCH v3 4/8] nfsd: don't vet delegated times against an exclusive-create verifier

[Jeff Layton <jlayton@kernel.org>]

An exclusive create stores the client's verifier in atime and mtime
until the client sets real times. A delegation granted on that OPEN
records those as dl_atime and dl_mtime (e.g. 4777.0 and 681509.0), so
vetting the holder's times against them always passes, including times
older than the file itself.

When the OPEN did an exclusive create, use the ctime at grant, less 1ns,
as the floor for atime and mtime too. Vetting rejects a time equal to
its floor, and a holder time equal to the ctime must still replace the
verifier. Do this for both write and read timestamp delegations, and
set a read delegation's floors only when the stat behind them was
done. Move nfsd4_create_is_exclusive() to xdr4.h so nfs4state.c can use
it.

Fixes: 7663e963a511 ("nfsd: track original timestamps in nfs4_delegation")
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfsd/nfs4proc.c  |  6 ------
 fs/nfsd/nfs4state.c | 27 +++++++++++++++++++++++----
 fs/nfsd/xdr4.h      |  6 ++++++
 3 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 4e5d5852bf57..25613c1ffaaf 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -245,12 +245,6 @@ static void nfsd4_set_open_owner_reply_cache(struct nfsd4_compound_state *cstate
 			&resfh->fh_handle);
 }
 
-static inline bool nfsd4_create_is_exclusive(int createmode)
-{
-	return createmode == NFS4_CREATE_EXCLUSIVE ||
-		createmode == NFS4_CREATE_EXCLUSIVE4_1;
-}
-
 static struct file *do_lookup_open(struct path *parent,
 				   struct qstr *name,
 				   unsigned int oflags,
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 35712e129b7a..4566fa86f82f 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -7466,6 +7466,26 @@ nfsd4_add_rdaccess_to_wrdeleg(struct svc_rqst *rqstp, struct nfsd4_open *open,
 	return true;
 }
 
+/*
+ * An exclusive create stores the verifier in atime and mtime, so the only
+ * real floor for the holder's times is the ctime. Vetting rejects a time
+ * equal to its floor, but one equal to the ctime must still replace the
+ * verifier.
+ */
+static void nfsd4_deleg_set_time_floors(struct nfs4_delegation *dp,
+					const struct nfsd4_open *open,
+					const struct kstat *stat)
+{
+	dp->dl_atime = stat->atime;
+	dp->dl_ctime = stat->ctime;
+	dp->dl_mtime = stat->mtime;
+	if (open->op_created &&
+	    nfsd4_create_is_exclusive(open->op_createmode)) {
+		dp->dl_atime = timespec64_sub(stat->ctime, ns_to_timespec64(1));
+		dp->dl_mtime = dp->dl_atime;
+	}
+}
+
 /*
  * The Linux NFS server does not offer write delegations to NFSv4.0
  * clients in order to avoid conflicts between write delegations and
@@ -7556,9 +7576,7 @@ nfs4_open_delegation(struct svc_rqst *rqstp, struct nfsd4_open *open,
 						    OPEN_DELEGATE_WRITE;
 		dp->dl_cb_fattr.ncf_initial_cinfo = nfsd4_change_attribute(&stat);
 		dp->dl_cb_fattr.ncf_srv_cinfo = dp->dl_cb_fattr.ncf_initial_cinfo;
-		dp->dl_atime = stat.atime;
-		dp->dl_ctime = stat.ctime;
-		dp->dl_mtime = stat.mtime;
+		nfsd4_deleg_set_time_floors(dp, open, &stat);
 		spin_lock(&f->f_lock);
 		if (deleg_ts)
 			f->f_mode |= FMODE_NOCMTIME;
@@ -7567,7 +7585,8 @@ nfs4_open_delegation(struct svc_rqst *rqstp, struct nfsd4_open *open,
 	} else {
 		open->op_delegate_type = deleg_ts && nfs4_delegation_stat(dp, currentfh, &stat) ?
 					 OPEN_DELEGATE_READ_ATTRS_DELEG : OPEN_DELEGATE_READ;
-		dp->dl_atime = stat.atime;
+		if (open->op_delegate_type == OPEN_DELEGATE_READ_ATTRS_DELEG)
+			nfsd4_deleg_set_time_floors(dp, open, &stat);
 		trace_nfsd_deleg_read(&dp->dl_stid.sc_stateid);
 	}
 	nfs4_put_stid(&dp->dl_stid);
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index ecab2249e9bd..feda5464f260 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -280,6 +280,12 @@ struct nfsd4_open {
 	struct svc_rqst *op_rqstp;
 };
 
+static inline bool nfsd4_create_is_exclusive(int createmode)
+{
+	return createmode == NFS4_CREATE_EXCLUSIVE ||
+		createmode == NFS4_CREATE_EXCLUSIVE4_1;
+}
+
 struct nfsd4_open_confirm {
 	stateid_t	oc_req_stateid		/* request */;
 	u32		oc_seqid    		/* request */;

-- 
2.56.0