From patchwork Thu Sep 1 19:10:24 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever X-Patchwork-Id: 12963137 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF0EFECAAD1 for ; Thu, 1 Sep 2022 19:10:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232987AbiIATK3 (ORCPT ); Thu, 1 Sep 2022 15:10:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47650 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233567AbiIATK3 (ORCPT ); Thu, 1 Sep 2022 15:10:29 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5B96D4A821 for ; Thu, 1 Sep 2022 12:10:28 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 1842DB828FF for ; Thu, 1 Sep 2022 19:10:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9E7EC433D6; Thu, 1 Sep 2022 19:10:25 +0000 (UTC) Subject: [PATCH v3 6/6] NFSD: Protect against send buffer overflow in NFSv3 READ From: Chuck Lever To: linux-nfs@vger.kernel.org Date: Thu, 01 Sep 2022 15:10:24 -0400 Message-ID: <166205942489.1435.8984764212504461615.stgit@manet.1015granger.net> In-Reply-To: <166204973526.1435.6068003336048840051.stgit@manet.1015granger.net> References: <166204973526.1435.6068003336048840051.stgit@manet.1015granger.net> User-Agent: StGit/1.5.dev2+g9ce680a5 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org Since before the git era, NFSD has conserved the number of pages held by each nfsd thread by combining the RPC receive and send buffers into a single array of pages. This works because there are no cases where an operation needs a large RPC Call message and a large RPC Reply at the same time. Once an RPC Call has been received, svc_process() updates svc_rqst::rq_res to describe the part of rq_pages that can be used for constructing the Reply. This means that the send buffer (rq_res) shrinks when the received RPC record containing the RPC Call is large. A client can force this shrinkage on TCP by sending a correctly- formed RPC Call header contained in an RPC record that is excessively large. The full maximum payload size cannot be constructed in that case. Cc: Signed-off-by: Chuck Lever Reviewed-by: Jeff Layton --- fs/nfsd/nfs3proc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c index 7a159785499a..5b1e771238b3 100644 --- a/fs/nfsd/nfs3proc.c +++ b/fs/nfsd/nfs3proc.c @@ -150,7 +150,6 @@ nfsd3_proc_read(struct svc_rqst *rqstp) { struct nfsd3_readargs *argp = rqstp->rq_argp; struct nfsd3_readres *resp = rqstp->rq_resp; - u32 max_blocksize = svc_max_payload(rqstp); unsigned int len; int v; @@ -159,7 +158,8 @@ nfsd3_proc_read(struct svc_rqst *rqstp) (unsigned long) argp->count, (unsigned long long) argp->offset); - argp->count = min_t(u32, argp->count, max_blocksize); + argp->count = min_t(u32, argp->count, svc_max_payload(rqstp)); + argp->count = min_t(u32, argp->count, rqstp->rq_res.buflen); if (argp->offset > (u64)OFFSET_MAX) argp->offset = (u64)OFFSET_MAX; if (argp->offset + argp->count > (u64)OFFSET_MAX)