nfsd4: Handle the NFSv4 READDIR 'dircount' hint being zero

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>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index b16a6c03635270fb49cd986473b5d9eff8d16b25..dc51011d670dfa201be8ce0ecf74e568f083d5cb 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3028,15 +3028,18 @@ nfsd4_encode_dirent(void *ccdv, const char *name, int namlen,
                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: