From patchwork Tue Mar 23 22:48:58 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 12159835 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-21.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CE2BC433DB for ; Tue, 23 Mar 2021 23:53:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CC67561993 for ; Tue, 23 Mar 2021 23:53:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231277AbhCWXtO (ORCPT ); Tue, 23 Mar 2021 19:49:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:55680 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231202AbhCWXtH (ORCPT ); Tue, 23 Mar 2021 19:49:07 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9F7DF619C2; Tue, 23 Mar 2021 23:49:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616543343; bh=73IUD1ex775GRIOLkVkhFhRaIXgVYqgtUbryJLv3RBw=; h=Date:From:To:Cc:Subject:From; b=GnFKBWJxIKnz95O+xW2aV0ZoO+k4AppcoqQoxYdGISN46/avmkjUr1OJ+PvHv0j+2 uWgNXseJrkWz5+3fcH3U20pHkOk1r2rvKM0otZMCqoJb55HRO0QPHywCp4DurK9KLO E8z1w8rszrCzPrmmi9/9bxVbqtb34N+ygZmKqLRNFYTcbnl7vZOGPJBnxHEs6cnWN/ FAaFR/NPi5BEYFPt/0lj8UfVHj5BqqUV795/9cfo//R7e3vXLV/+wnPqIo+mpHuEUy dOoYrYuq+CVhVLtM1sQG9Va+lD2sL+s80irx22HvpKfoemVnosCu51bWGRDIxVrFt2 vFVXdAo0v8e0w== Date: Tue, 23 Mar 2021 17:48:58 -0500 From: "Gustavo A. R. Silva" To: "J. Bruce Fields" , Chuck Lever Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" , linux-hardening@vger.kernel.org Subject: [PATCH][next] UAPI: nfsfh.h: Replace one-element array with flexible-array member Message-ID: <20210323224858.GA293698@embeddedor> MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. Use an anonymous union with a couple of anonymous structs in order to keep userspace unchanged: $ pahole -C nfs_fhbase_new fs/nfsd/nfsfh.o struct nfs_fhbase_new { union { struct { __u8 fb_version_aux; /* 0 1 */ __u8 fb_auth_type_aux; /* 1 1 */ __u8 fb_fsid_type_aux; /* 2 1 */ __u8 fb_fileid_type_aux; /* 3 1 */ __u32 fb_auth[1]; /* 4 4 */ }; /* 0 8 */ struct { __u8 fb_version; /* 0 1 */ __u8 fb_auth_type; /* 1 1 */ __u8 fb_fsid_type; /* 2 1 */ __u8 fb_fileid_type; /* 3 1 */ __u32 fb_auth_flex[0]; /* 4 0 */ }; /* 0 4 */ }; /* 0 8 */ /* size: 8, cachelines: 1, members: 1 */ /* last cacheline: 8 bytes */ }; Also, this helps with the ongoing efforts to enable -Warray-bounds by fixing the following warnings: fs/nfsd/nfsfh.c: In function ‘nfsd_set_fh_dentry’: fs/nfsd/nfsfh.c:191:41: warning: array subscript 1 is above array bounds of ‘__u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds] 191 | ntohl((__force __be32)fh->fh_fsid[1]))); | ~~~~~~~~~~~^~~ ./include/linux/kdev_t.h:12:46: note: in definition of macro ‘MKDEV’ 12 | #define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi)) | ^~ ./include/uapi/linux/byteorder/little_endian.h:40:26: note: in expansion of macro ‘__swab32’ 40 | #define __be32_to_cpu(x) __swab32((__force __u32)(__be32)(x)) | ^~~~~~~~ ./include/linux/byteorder/generic.h:136:21: note: in expansion of macro ‘__be32_to_cpu’ 136 | #define ___ntohl(x) __be32_to_cpu(x) | ^~~~~~~~~~~~~ ./include/linux/byteorder/generic.h:140:18: note: in expansion of macro ‘___ntohl’ 140 | #define ntohl(x) ___ntohl(x) | ^~~~~~~~ fs/nfsd/nfsfh.c:191:8: note: in expansion of macro ‘ntohl’ 191 | ntohl((__force __be32)fh->fh_fsid[1]))); | ^~~~~ fs/nfsd/nfsfh.c:192:32: warning: array subscript 2 is above array bounds of ‘__u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds] 192 | fh->fh_fsid[1] = fh->fh_fsid[2]; | ~~~~~~~~~~~^~~ fs/nfsd/nfsfh.c:192:15: warning: array subscript 1 is above array bounds of ‘__u32[1]’ {aka ‘unsigned int[1]’} [-Warray-bounds] 192 | fh->fh_fsid[1] = fh->fh_fsid[2]; | ~~~~~~~~~~~^~~ [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays Link: https://github.com/KSPP/linux/issues/79 Link: https://github.com/KSPP/linux/issues/109 Signed-off-by: Gustavo A. R. Silva --- include/uapi/linux/nfsd/nfsfh.h | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/include/uapi/linux/nfsd/nfsfh.h b/include/uapi/linux/nfsd/nfsfh.h index ff0ca88b1c8f..427294dd56a1 100644 --- a/include/uapi/linux/nfsd/nfsfh.h +++ b/include/uapi/linux/nfsd/nfsfh.h @@ -64,13 +64,24 @@ struct nfs_fhbase_old { * in include/linux/exportfs.h for currently registered values. */ struct nfs_fhbase_new { - __u8 fb_version; /* == 1, even => nfs_fhbase_old */ - __u8 fb_auth_type; - __u8 fb_fsid_type; - __u8 fb_fileid_type; - __u32 fb_auth[1]; -/* __u32 fb_fsid[0]; floating */ -/* __u32 fb_fileid[0]; floating */ + union { + struct { + __u8 fb_version_aux; /* == 1, even => nfs_fhbase_old */ + __u8 fb_auth_type_aux; + __u8 fb_fsid_type_aux; + __u8 fb_fileid_type_aux; + __u32 fb_auth[1]; + /* __u32 fb_fsid[0]; floating */ + /* __u32 fb_fileid[0]; floating */ + }; + struct { + __u8 fb_version; /* == 1, even => nfs_fhbase_old */ + __u8 fb_auth_type; + __u8 fb_fsid_type; + __u8 fb_fileid_type; + __u32 fb_auth_flex[]; /* flexible-array member */ + }; + }; }; struct knfsd_fh { @@ -97,7 +108,7 @@ struct knfsd_fh { #define fh_fsid_type fh_base.fh_new.fb_fsid_type #define fh_auth_type fh_base.fh_new.fb_auth_type #define fh_fileid_type fh_base.fh_new.fb_fileid_type -#define fh_fsid fh_base.fh_new.fb_auth +#define fh_fsid fh_base.fh_new.fb_auth_flex /* Do not use, provided for userspace compatiblity. */ #define fh_auth fh_base.fh_new.fb_auth