--- /dev/null
+From f2e717d655040d632c9015f19aa4275f8b16e7f2 Mon Sep 17 00:00:00 2001
+From: Trond Myklebust <trond.myklebust@hammerspace.com>
+Date: Thu, 30 Sep 2021 15:44:41 -0400
+Subject: nfsd4: Handle the NFSv4 READDIR 'dircount' hint being zero
+
+From: Trond Myklebust <trond.myklebust@hammerspace.com>
+
+commit f2e717d655040d632c9015f19aa4275f8b16e7f2 upstream.
+
+RFC3530 notes that the 'dircount' field may be zero, in which case the
+recommendation is to ignore it, and only enforce the 'maxcount' field.
+In RFC5661, this recommendation to ignore a zero valued field becomes a
+requirement.
+
+Fixes: aee377644146 ("nfsd4: fix rd_dircount enforcement")
+Cc: <stable@vger.kernel.org>
+Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
+Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ fs/nfsd/nfs4xdr.c | 19 +++++++++++--------
+ 1 file changed, 11 insertions(+), 8 deletions(-)
+
+--- a/fs/nfsd/nfs4xdr.c
++++ b/fs/nfsd/nfs4xdr.c
+@@ -2988,15 +2988,18 @@ nfsd4_encode_dirent(void *ccdv, const ch
+ goto fail;
+ cd->rd_maxcount -= entry_bytes;
+ /*
+- * RFC 3530 14.2.24 describes rd_dircount as only a "hint", so
+- * let's always let through the first entry, at least:
++ * RFC 3530 14.2.24 describes rd_dircount as only a "hint", and
++ * notes that it could be zero. If it is zero, then the server
++ * should enforce only the rd_maxcount value.
+ */
+- if (!cd->rd_dircount)
+- goto fail;
+- name_and_cookie = 4 + 4 * XDR_QUADLEN(namlen) + 8;
+- if (name_and_cookie > cd->rd_dircount && cd->cookie_offset)
+- goto fail;
+- cd->rd_dircount -= min(cd->rd_dircount, name_and_cookie);
++ if (cd->rd_dircount) {
++ name_and_cookie = 4 + 4 * XDR_QUADLEN(namlen) + 8;
++ if (name_and_cookie > cd->rd_dircount && cd->cookie_offset)
++ goto fail;
++ cd->rd_dircount -= min(cd->rd_dircount, name_and_cookie);
++ if (!cd->rd_dircount)
++ cd->rd_maxcount = 0;
++ }
+
+ cd->cookie_offset = cookie_offset;
+ skip_entry: