nfsd: fix handling of readdir in v4root vs. mount upcall timeout

commit cad853374d85fe678d721512cecfabd7636e51f3 upstream.

If v4 READDIR operation hits a mountpoint and gets back an error,
then it will include that entry in the reply and set RDATTR_ERROR for it
to the error.

That's fine for "normal" exported filesystems, but on the v4root, we
need to be more careful to only expose the existence of dentries that
lead to exports.

If the mountd upcall times out while checking to see whether a
mountpoint on the v4root is exported, then we have no recourse other
than to fail the whole operation.

Cc: Steve Dickson <steved@redhat.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216777
Reported-by: JianHong Yin <yin-jianhong@163.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 95bbe9d4018aa6bccdd9ad7cef4c8bed7682ce46..a4f2c0cc6a49e1626bc4108d263e8308ed2f1f9c 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3109,6 +3109,17 @@ nfsd4_encode_dirent(void *ccdv, const char *name, int namlen,
        case nfserr_noent:
                xdr_truncate_encode(xdr, start_offset);
                goto skip_entry;
+       case nfserr_jukebox:
+               /*
+                * The pseudoroot should only display dentries that lead to
+                * exports. If we get EJUKEBOX here, then we can't tell whether
+                * this entry should be included. Just fail the whole READDIR
+                * with NFS4ERR_DELAY in that case, and hope that the situation
+                * will resolve itself by the client's next attempt.
+                */
+               if (cd->rd_fhp->fh_export->ex_flags & NFSEXP_V4ROOT)
+                       goto fail;
+               fallthrough;
        default:
                /*
                 * If the client requested the RDATTR_ERROR attribute,