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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Scott Mayhew" <smayhew@redhat.com>,
        "J. Bruce Fields" <bfields@redhat.com>
Date:   Sun, 11 Nov 2018 19:49:05 +0000
Message-ID: <lsq.1541965745.79942609@decadent.org.uk>
Subject: [PATCH 3.16 035/366] nfsd: restrict rd_maxcount to
 svc_max_payload in nfsd_encode_readdir
In-Reply-To: <lsq.1541965744.387173642@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.61-rc1 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>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 fs/nfsd/nfs4xdr.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3343,7 +3343,8 @@ 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
@@ -3357,7 +3358,7 @@ 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;