[PATCH v6 20/20] nfsd: add support to CB_NOTIFY for dir attribute changes

[Jeff Layton <jlayton@kernel.org>]

If the client requested dir attribute change notifications, send those
alongside any set of add/remove/rename events. Note that the server will
still recall the delegation on a SETATTR, so these are only sent for
changes to child dirents.

The child filehandle returned in these notifications is composed by
setup_notify_fhandle() without going through fh_compose(), so it does
not get a MAC appended. On exports configured with NFSEXP_SIGN_FH the
client would then get back an unsigned filehandle that fh_verify()
rejects as stale. Pass the delegation's export down to
setup_notify_fhandle() and append the MAC with fh_append_mac() when the
export requires signed filehandles; if signing fails, drop the
filehandle attribute rather than handing out an unusable one.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfsd/nfs4state.c | 25 ++++++++++++++++--
 fs/nfsd/nfs4xdr.c   | 73 +++++++++++++++++++++++++++++++++++++++++++++--------
 fs/nfsd/xdr4.h      |  2 ++
 3 files changed, 88 insertions(+), 12 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 12627afb604f..e394278fb92e 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3503,10 +3503,15 @@ nfsd4_cb_notify_prepare(struct nfsd4_callback *cb)
 	struct nfsd_notify_event *events[NOTIFY4_EVENT_QUEUE_SIZE];
 	struct xdr_buf xdr = { .buflen = PAGE_SIZE * NOTIFY4_PAGE_ARRAY_SIZE,
 			       .pages  = ncn->ncn_pages };
+	int limit = NOTIFY4_EVENT_QUEUE_SIZE;
 	struct xdr_stream stream;
 	struct nfsd_file *nf;
-	int count, i;
 	bool error = false;
+	int count, i;
+
+	/* Save a slot for dir attr update if requested */
+	if (dp->dl_notify_mask & BIT(NOTIFY4_CHANGE_DIR_ATTRS))
+		--limit;
 
 	xdr_init_encode_pages(&stream, &xdr);
 
@@ -3520,7 +3525,7 @@ nfsd4_cb_notify_prepare(struct nfsd4_callback *cb)
 	}
 
 	/* we can't keep up! */
-	if (count > NOTIFY4_EVENT_QUEUE_SIZE) {
+	if (count > limit) {
 		spin_unlock(&ncn->ncn_lock);
 		goto out_recall;
 	}
@@ -3567,6 +3572,22 @@ nfsd4_cb_notify_prepare(struct nfsd4_callback *cb)
 		nfsd_notify_event_put(nne);
 	}
 	if (!error) {
+		if (dp->dl_notify_mask & BIT(NOTIFY4_CHANGE_DIR_ATTRS)) {
+			u32 *maskp = (u32 *)xdr_reserve_space(&stream, sizeof(*maskp));
+
+			if (maskp) {
+				u8 *p = nfsd4_encode_dir_attr_change(&stream, dp, nf);
+
+				if (p) {
+					*maskp = BIT(NOTIFY4_CHANGE_DIR_ATTRS);
+					ncn->ncn_nf[count].notify_mask.count = 1;
+					ncn->ncn_nf[count].notify_mask.element = maskp;
+					ncn->ncn_nf[count].notify_vals.data = p;
+					ncn->ncn_nf[count].notify_vals.len = (u8 *)stream.p - p;
+					++count;
+				}
+			}
+		}
 		ncn->ncn_nf_cnt = count;
 		nfsd_file_put(nf);
 		return true;
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 1e3c360c06cd..7dd8476028d6 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -4199,7 +4199,8 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
 
 static bool
 setup_notify_fhandle(struct dentry *dentry, struct nfs4_file *fi,
-		     struct nfsd_file *nf, struct nfsd4_fattr_args *args)
+		     struct nfsd_file *nf, struct svc_export *exp,
+		     struct nfsd4_fattr_args *args)
 {
 	int fileid_type, fsid_len, maxsize, flags = 0;
 	struct knfsd_fh *fhp = &args->fhandle;
@@ -4227,6 +4228,17 @@ setup_notify_fhandle(struct dentry *dentry, struct nfs4_file *fi,
 
 	fhp->fh_fileid_type = fileid_type;
 	fhp->fh_size += maxsize * 4;
+
+	/*
+	 * fh_compose() appends a MAC to filehandles on signed exports; this
+	 * hand-rolled filehandle must do the same or the client will get back
+	 * an unsigned filehandle that fh_verify() later rejects as stale.
+	 * If we can't sign it, don't hand it out at all.
+	 */
+	if (exp && (exp->ex_flags & NFSEXP_SIGN_FH))
+		if (!fh_append_mac(fhp, NFS4_FHSIZE, exp->cd->net))
+			return false;
+
 	return true;
 }
 
@@ -4240,11 +4252,11 @@ nfsd4_setup_notify_entry4(struct notify_entry4 *ne, struct xdr_stream *xdr,
 			  struct nfsd_file *nf, char *name, u32 namelen)
 {
 	struct nfs4_file *fi = dp->dl_stid.sc_file;
-	struct path path =  { .mnt = nf->nf_file->f_path.mnt,
-			      .dentry = dentry };
+	struct path path = nf->nf_file->f_path;
 	struct nfsd4_fattr_args args = { };
 	uint32_t *attrmask;
 	__be32 status;
+	bool parent;
 	int ret;
 
 	/* Reserve space for attrmask */
@@ -4256,6 +4268,9 @@ nfsd4_setup_notify_entry4(struct notify_entry4 *ne, struct xdr_stream *xdr,
 	ne->ne_file.len = namelen;
 	ne->ne_attrs.attrmask.element = attrmask;
 
+	parent = (dentry == path.dentry);
+	path.dentry = dentry;
+
 	/* FIXME: d_find_alias for inode ? */
 	if (!path.dentry || !d_inode(path.dentry))
 		goto noattrs;
@@ -4271,15 +4286,21 @@ nfsd4_setup_notify_entry4(struct notify_entry4 *ne, struct xdr_stream *xdr,
 
 	args.change_attr = nfsd4_change_attribute(&args.stat);
 
-	attrmask[0] = dp->dl_child_attrs[0];
-	attrmask[1] = dp->dl_child_attrs[1];
-	attrmask[2] = 0;
+	if (parent) {
+		attrmask[0] = dp->dl_dir_attrs[0];
+		attrmask[1] = dp->dl_dir_attrs[1];
+	} else {
+		attrmask[0] = dp->dl_child_attrs[0];
+		attrmask[1] = dp->dl_child_attrs[1];
 
-	if (!setup_notify_fhandle(dentry, fi, nf, &args))
-		attrmask[0] &= ~FATTR4_WORD0_FILEHANDLE;
+		if (!setup_notify_fhandle(dentry, fi, nf,
+					  dp->dl_stid.sc_export, &args))
+			attrmask[0] &= ~FATTR4_WORD0_FILEHANDLE;
 
-	if (!(args.stat.result_mask & STATX_BTIME))
-		attrmask[1] &= ~FATTR4_WORD1_TIME_CREATE;
+		if (!(args.stat.result_mask & STATX_BTIME))
+			attrmask[1] &= ~FATTR4_WORD1_TIME_CREATE;
+	}
+	attrmask[2] = 0;
 
 	ne->ne_attrs.attrmask.count = 2;
 	ne->ne_attrs.attr_vals.data = (u8 *)xdr->p;
@@ -4392,6 +4413,38 @@ u8 *nfsd4_encode_notify_event(struct xdr_stream *xdr, struct nfsd_notify_event *
 	return NULL;
 }
 
+/**
+ * nfsd4_encode_dir_attr_change
+ * @xdr: stream to which to encode the fattr4
+ * @dp: delegation where the event occurred
+ * @nf: nfsd_file opened on the directory
+ *
+ * Encode a dir attr change event.
+ */
+u8 *nfsd4_encode_dir_attr_change(struct xdr_stream *xdr, struct nfs4_delegation *dp,
+				 struct nfsd_file *nf)
+{
+	struct dentry *dentry = nf->nf_file->f_path.dentry;
+	struct notify_attr4 na = { };
+	bool ret;
+	u8 *p = NULL;
+
+	if (!(dp->dl_notify_mask & BIT(NOTIFY4_CHANGE_DIR_ATTRS)))
+		return NULL;
+
+	/* RFC 8881 s10.4.3: ne_file must be a zero-length string for dir attrs */
+	ret = nfsd4_setup_notify_entry4(&na.na_changed_entry, xdr,
+					dentry, dp, nf, "", 0);
+
+	/* Don't bother with the event if we're not encoding attrs */
+	if (ret && na.na_changed_entry.ne_attrs.attr_vals.len) {
+		p = (u8 *)xdr->p;
+		if (!xdrgen_encode_notify_attr4(xdr, &na))
+			p = NULL;
+	}
+	return p;
+}
+
 static void svcxdr_init_encode_from_buffer(struct xdr_stream *xdr,
 				struct xdr_buf *buf, __be32 *p, int bytes)
 {
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 62ac790428be..805c7122eb93 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -973,6 +973,8 @@ __be32 nfsd4_encode_fattr_to_buf(__be32 **p, int words,
 u8 *nfsd4_encode_notify_event(struct xdr_stream *xdr, struct nfsd_notify_event *nne,
 			      struct nfs4_delegation *dd, struct nfsd_file *nf,
 			      u32 *notify_mask);
+u8 *nfsd4_encode_dir_attr_change(struct xdr_stream *xdr, struct nfs4_delegation *dp,
+				 struct nfsd_file *nf);
 extern __be32 nfsd4_setclientid(struct svc_rqst *rqstp,
 		struct nfsd4_compound_state *, union nfsd4_op_u *u);
 extern __be32 nfsd4_setclientid_confirm(struct svc_rqst *rqstp,

-- 
2.54.0