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 db0beefe65ec2c0613c4348dd09aabcaa039314c..f67c5de1aeb8d19955c51a59a5d2e00484096034 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3124,15 +3124,18 @@ 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: