From patchwork Wed Nov 20 19:13:15 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever X-Patchwork-Id: 13881406 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0EEE91B3B2E; Wed, 20 Nov 2024 19:13:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732130000; cv=none; b=NZQ48H3FSyYZVK9NbR97PWWkySzmi09fEgAebezPy+kH5d7A0TotTiMedqu7tVFoHpiAAwhofBufGnGg8Q8c4mPBzaneis5ZvNExII/OSebkEa+3IwykB3QFW0ZLaa1i+H+DWK/9BDT8/bII+UmjBo7OiLVBPGNd+MVUWZqoGbk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732130000; c=relaxed/simple; bh=xAaH516sluP+p27RS0Mw2WOm62v1bm2TiJ9WqLzPOh8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZTHNt+1DQwa1bOrSyFN4q2erRKECuac8AVrOOW7/DsojhLYHz2/IZFQYMdglcyfJmexCvOgYPJL89osTp4o8PjHhkX/mYPSyXA8BsV+eiAo1lk5pJZcsgq4xvSrm/KGRqgeKZMxaQ7UmM4BjNi/WCUAYtSDvP1DnTsz2FBmdmvQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dwMxZBGL; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dwMxZBGL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1FA1EC4CED3; Wed, 20 Nov 2024 19:13:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732129999; bh=xAaH516sluP+p27RS0Mw2WOm62v1bm2TiJ9WqLzPOh8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dwMxZBGL11ORSibGN4eeeWTUQWNIdgDTQaL/lw6VhdZ9d2wRkWWs2Snn8MqNO36Xs SbtCVKvomIDcYYHfba1p9M93Z/gVG8t4cAPO2f1x2Rnne41TbRuf2X3YDygL1K9DUU ISEOVH5z9J1IZXqwGKu69eKACGcd68CnkKS9xgAeb5+Pz2bTLUX/UZN1j4jX4Z9yj0 KRJbqK48usj4YOXw1JZezam7YxImOHaifAlK/Bt7xA3B82GlVJ6XW6b1WBTwtUrMov BwH0MtIVGObQcgWw/Unwy+gW4GYxSvjWbIfMwLEPhhJ7kfAo0/UPZK3tgEUd7woPU2 UIerZMVMnEf+A== From: cel@kernel.org To: Cc: , Jeff Layton , Chuck Lever Subject: [PATCH 5.4] NFSD: Force all NFSv4.2 COPY requests to be synchronous Date: Wed, 20 Nov 2024 14:13:15 -0500 Message-ID: <20241120191315.6907-2-cel@kernel.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241120191315.6907-1-cel@kernel.org> References: <20241120191315.6907-1-cel@kernel.org> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Chuck Lever [ Upstream commit 8d915bbf39266bb66082c1e4980e123883f19830 ] We've discovered that delivering a CB_OFFLOAD operation can be unreliable in some pretty unremarkable situations. Examples include: - The server dropped the connection because it lost a forechannel NFSv4 request and wishes to force the client to retransmit - The GSS sequence number window under-flowed - A network partition occurred When that happens, all pending callback operations, including CB_OFFLOAD, are lost. NFSD does not retransmit them. Moreover, the Linux NFS client does not yet support sending an OFFLOAD_STATUS operation to probe whether an asynchronous COPY operation has finished. Thus, on Linux NFS clients, when a CB_OFFLOAD is lost, asynchronous COPY can hang until manually interrupted. I've tried a couple of remedies, but so far the side-effects are worse than the disease and they have had to be reverted. So temporarily force COPY operations to be synchronous so that the use of CB_OFFLOAD is avoided entirely. This is a fix that can easily be backported to LTS kernels. I am working on client patches that introduce an implementation of OFFLOAD_STATUS. Note that NFSD arbitrarily limits the size of a copy_file_range to 4MB to avoid indefinitely blocking an nfsd thread. A short COPY result is returned in that case, and the client can present a fresh COPY request for the remainder. Link: https://nvd.nist.gov/vuln/detail/CVE-2024-49974 [ cel: adjusted to apply to origin/linux-5.4.y ] Signed-off-by: Chuck Lever --- fs/nfsd/nfs4proc.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c index e38f873f98a7..27e9754ad3b9 100644 --- a/fs/nfsd/nfs4proc.c +++ b/fs/nfsd/nfs4proc.c @@ -1262,6 +1262,13 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, __be32 status; struct nfsd4_copy *async_copy = NULL; + /* + * Currently, async COPY is not reliable. Force all COPY + * requests to be synchronous to avoid client application + * hangs waiting for COPY completion. + */ + copy->cp_synchronous = 1; + status = nfsd4_verify_copy(rqstp, cstate, ©->cp_src_stateid, ©->nf_src, ©->cp_dst_stateid, ©->nf_dst);