1 files changed, 10 insertions, 2 deletions

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 04bdba12d21b..7e2fdd50113f 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -99,8 +99,16 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
 
         exp2 = rqst_exp_get_by_name(rqstp, &path);
         if (IS_ERR(exp2)) {
-                if (PTR_ERR(exp2) != -ENOENT)
-                        err = PTR_ERR(exp2);
+                err = PTR_ERR(exp2);
+                /*
+                 * We normally allow NFS clients to continue
+                 * "underneath" a mountpoint that is not exported.
+                 * The exception is V4ROOT, where no traversal is ever
+                 * allowed without an explicit export of the new
+                 * directory.
+                 */
+                if (err == -ENOENT && !(exp->ex_flags & NFSEXP_V4ROOT))
+                        err = 0;
                 path_put(&path);
                 goto out;
         }