[PATCH 4.9 084/101] nfsd: restrict rd_maxcount to svc_max_payload in nfsd_encode_readdir

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Scott Mayhew <smayhew@redhat.com>

commit 9c2ece6ef67e9d376f32823086169b489c422ed0 upstream.

nfsd4_readdir_rsize restricts rd_maxcount to svc_max_payload when
estimating the size of the readdir reply, but nfsd_encode_readdir
restricts it to INT_MAX when encoding the reply.  This can result in log
messages like "kernel: RPC request reserved 32896 but used 1049444".

Restrict rd_dircount similarly (no reason it should be larger than
svc_max_payload).

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/nfsd/nfs4xdr.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3638,7 +3638,8 @@ nfsd4_encode_readdir(struct nfsd4_compou
 		nfserr = nfserr_resource;
 		goto err_no_verf;
 	}
-	maxcount = min_t(u32, readdir->rd_maxcount, INT_MAX);
+	maxcount = svc_max_payload(resp->rqstp);
+	maxcount = min_t(u32, readdir->rd_maxcount, maxcount);
 	/*
 	 * Note the rfc defines rd_maxcount as the size of the
 	 * READDIR4resok structure, which includes the verifier above
@@ -3652,7 +3653,7 @@ nfsd4_encode_readdir(struct nfsd4_compou
 
 	/* RFC 3530 14.2.24 allows us to ignore dircount when it's 0: */
 	if (!readdir->rd_dircount)
-		readdir->rd_dircount = INT_MAX;
+		readdir->rd_dircount = svc_max_payload(resp->rqstp);
 
 	readdir->xdr = xdr;
 	readdir->rd_maxcount = maxcount;