[PATCH 2/4] nfsd: use empty string for directory name in NOTIFY4_CHANGE_DIR_ATTRS

[Jeff Layton]

RFC 8881 Section 10.4.3 specifies that for NOTIFY4_CHANGE_DIR_ATTRS
events, the ne_file component name must be a zero-length string. The
code was incorrectly using the directory's own dentry name, which
could leak the local namespace to the client and cause cache
confusion.

Pass an empty string and zero length instead, and remove the
now-unnecessary name_snapshot.

Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
 fs/nfsd/nfs4xdr.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 2f8d26601581..c6c50c376b23 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -4404,17 +4404,15 @@ u8 *nfsd4_encode_dir_attr_change(struct xdr_stream *xdr, struct nfs4_delegation
 {
 	struct dentry *dentry = nf->nf_file->f_path.dentry;
 	struct notify_attr4 na = { };
-	struct name_snapshot n;
 	bool ret;
 	u8 *p = NULL;
 
 	if (!(dp->dl_notify_mask & BIT(NOTIFY4_CHANGE_DIR_ATTRS)))
 		return NULL;
 
-	take_dentry_name_snapshot(&n, dentry);
+	/* 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, (char *)n.name.name,
-					n.name.len);
+					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) {
@@ -4422,7 +4420,6 @@ u8 *nfsd4_encode_dir_attr_change(struct xdr_stream *xdr, struct nfs4_delegation
 		if (!xdrgen_encode_notify_attr4(xdr, &na))
 			p = NULL;
 	}
-	release_dentry_name_snapshot(&n);
 	return p;
 }
 

-- 
2.54.0