From patchwork Fri Mar 6 22:17:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 11424767 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 200D01580 for ; Fri, 6 Mar 2020 23:01:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F3FE7206CC for ; Fri, 6 Mar 2020 23:01:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=embeddedor.com header.i=@embeddedor.com header.b="fe6wMZH1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726194AbgCFXBW (ORCPT ); Fri, 6 Mar 2020 18:01:22 -0500 Received: from gateway33.websitewelcome.com ([192.185.146.78]:44444 "EHLO gateway33.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726171AbgCFXBW (ORCPT ); Fri, 6 Mar 2020 18:01:22 -0500 X-Greylist: delayed 1500 seconds by postgrey-1.27 at vger.kernel.org; Fri, 06 Mar 2020 18:01:21 EST Received: from cm17.websitewelcome.com (cm17.websitewelcome.com [100.42.49.20]) by gateway33.websitewelcome.com (Postfix) with ESMTP id 67F1312004A for ; Fri, 6 Mar 2020 16:14:35 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id ALEpjaEn5AGTXALEpj2ZCX; Fri, 06 Mar 2020 16:14:35 -0600 X-Authority-Reason: nr=8 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=embeddedor.com; s=default; h=Content-Type:MIME-Version:Message-ID:Subject: Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=nBwlfiUJo4l1eGO3/VAyVjlX3AwTc9M2cRFum/DqUP4=; b=fe6wMZH1EP5Z1nRJw+m77yeD7Y LHTno/j6YfqvsizLS41Ci6tS5mt7f7WZwjCHdoj10jsWv5JkH/rFiKn9/IUbAsDhJ4d89Wcmdw5ZF ii3lzokrhXZgXuXny9XUOcAvzgK5MxSWqpaFLrPJ1yZwItR8q651NhjY32XLDJKeK5swMZoLx+1ho 6mFvOG70z8q3O2FUpe1KOOQaX0Simy1E4RWU7JvqgEKSXhAlVG1vcjt0A9vfctAV5Mw0qIKZclvWn zRQj5N1DwAnTND2B16g6sM43703jTsyo05l6qeztEPQRVgT2PIstsaExAaTQgXeSrb9tsljAcUTL5 ZZrMEvew==; Received: from [201.162.241.123] (port=6921 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1jALEm-000Jn7-UR; Fri, 06 Mar 2020 16:14:34 -0600 Date: Fri, 6 Mar 2020 16:17:40 -0600 From: "Gustavo A. R. Silva" To: Steve French Cc: linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] cifs: cifspdu.h: Replace zero-length array with flexible-array member Message-ID: <20200306221740.GA31410@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 201.162.241.123 X-Source-L: No X-Exim-ID: 1jALEm-000Jn7-UR X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.241.123]:6921 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 7 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-cifs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva --- fs/cifs/cifspdu.h | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h index 8e15887d1f1f..593d826820c3 100644 --- a/fs/cifs/cifspdu.h +++ b/fs/cifs/cifspdu.h @@ -1021,7 +1021,7 @@ typedef struct smb_com_writex_req { __le16 ByteCount; __u8 Pad; /* BB check for whether padded to DWORD boundary and optimum performance here */ - char Data[0]; + char Data[]; } __attribute__((packed)) WRITEX_REQ; typedef struct smb_com_write_req { @@ -1041,7 +1041,7 @@ typedef struct smb_com_write_req { __le16 ByteCount; __u8 Pad; /* BB check for whether padded to DWORD boundary and optimum performance here */ - char Data[0]; + char Data[]; } __attribute__((packed)) WRITE_REQ; typedef struct smb_com_write_rsp { @@ -1306,7 +1306,7 @@ typedef struct smb_com_ntransact_req { /* SetupCount words follow then */ __le16 ByteCount; __u8 Pad[3]; - __u8 Parms[0]; + __u8 Parms[]; } __attribute__((packed)) NTRANSACT_REQ; typedef struct smb_com_ntransact_rsp { @@ -1523,7 +1523,7 @@ struct file_notify_information { __le32 NextEntryOffset; __le32 Action; __le32 FileNameLength; - __u8 FileName[0]; + __u8 FileName[]; } __attribute__((packed)); /* For IO_REPARSE_TAG_SYMLINK */ @@ -1536,7 +1536,7 @@ struct reparse_symlink_data { __le16 PrintNameOffset; __le16 PrintNameLength; __le32 Flags; - char PathBuffer[0]; + char PathBuffer[]; } __attribute__((packed)); /* Flag above */ @@ -1553,7 +1553,7 @@ struct reparse_posix_data { __le16 ReparseDataLength; __u16 Reserved; __le64 InodeType; /* LNK, FIFO, CHR etc. */ - char PathBuffer[0]; + char PathBuffer[]; } __attribute__((packed)); struct cifs_quota_data { @@ -1762,7 +1762,7 @@ struct set_file_rename { __le32 overwrite; /* 1 = overwrite dest */ __u32 root_fid; /* zero */ __le32 target_name_len; - char target_name[0]; /* Must be unicode */ + char target_name[]; /* Must be unicode */ } __attribute__((packed)); struct smb_com_transaction2_sfi_req { @@ -2451,7 +2451,7 @@ struct cifs_posix_acl { /* access conrol list (ACL) */ __le16 version; __le16 access_entry_count; /* access ACL - count of entries */ __le16 default_entry_count; /* default ACL - count of entries */ - struct cifs_posix_ace ace_array[0]; + struct cifs_posix_ace ace_array[]; /* followed by struct cifs_posix_ace default_ace_arraay[] */ } __attribute__((packed)); /* level 0x204 */ @@ -2757,7 +2757,7 @@ typedef struct file_xattr_info { /* BB do we need another field for flags? BB */ __u32 xattr_name_len; __u32 xattr_value_len; - char xattr_name[0]; + char xattr_name[]; /* followed by xattr_value[xattr_value_len], no pad */ } __attribute__((packed)) FILE_XATTR_INFO; /* extended attribute info level 0x205 */