From patchwork Tue Feb 25 23:48:37 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: 11405043 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 CA15A14E3 for ; Wed, 26 Feb 2020 00:09:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9ED5A20732 for ; Wed, 26 Feb 2020 00:09:35 +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="LdFi92iG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729203AbgBZAJe (ORCPT ); Tue, 25 Feb 2020 19:09:34 -0500 Received: from gateway34.websitewelcome.com ([192.185.148.109]:45248 "EHLO gateway34.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728865AbgBZAJd (ORCPT ); Tue, 25 Feb 2020 19:09:33 -0500 X-Greylist: delayed 1423 seconds by postgrey-1.27 at vger.kernel.org; Tue, 25 Feb 2020 19:09:33 EST Received: from cm14.websitewelcome.com (cm14.websitewelcome.com [100.42.49.7]) by gateway34.websitewelcome.com (Postfix) with ESMTP id 8A6891209B20 for ; Tue, 25 Feb 2020 17:45:49 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 6jtdjq3MPXVkQ6jtdjBSPE; Tue, 25 Feb 2020 17:45:49 -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=8kpppuVxEfbw1HY9gBs/P7x/njX6QXOO1jMPxsNR6sQ=; b=LdFi92iGDpBZAOEsGks8AdD4mT auLnIL2SJ/JwRgBeofSCcegK3Uv5sAHC2DZfOZ2k2yOpHIy8hWmokqXZojvcnp5U5t5C18ared7y4 fH2sRDUIpzmxnyX/j2/hnOOcik3PohMovNqK/m2+9LZve2J6y71A7vYqydRumrArUNyeeiZ8k+gUX uGUwCFc0WJH2XLrMxyivzrz6wLTpe81q2ysj3PJv4emwPEmXQFMKNZqtHBF7iwdfZfOCfztLJPwzt ErqJagG72z1hQ/8Nx5Rj/HvJgsLQJLBqmtKcW47hVisLRS2ET9m5tGNkUYyb3VU1gTMnzPvHiH2UT 0cwKBDeQ==; Received: from [201.162.241.105] (port=30500 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j6jtb-001yzF-GN; Tue, 25 Feb 2020 17:45:48 -0600 Date: Tue, 25 Feb 2020 17:48:37 -0600 From: "Gustavo A. R. Silva" To: "Richard Russon (FlatCap)" , Jens Axboe , Philipp Reisner , Lars Ellenberg , Ilya Dryomov , Sage Weil , Dongsheng Yang Cc: linux-ntfs-dev@lists.sourceforge.net, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, drbd-dev@lists.linbit.com, ceph-devel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] block: Replace zero-length array with flexible-array member Message-ID: <20200225234836.GA31741@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: 201.162.241.105 X-Source-L: No X-Exim-ID: 1j6jtb-001yzF-GN X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.241.105]:30500 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 12 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: ceph-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: ceph-devel@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 Acked-by: Ilya Dryomov --- block/partitions/ldm.h | 2 +- drivers/block/drbd/drbd_int.h | 2 +- drivers/block/drbd/drbd_protocol.h | 8 ++++---- drivers/block/rbd_types.h | 2 +- 4 files changed, 7 insertions(+), 7 deletions(-) diff --git a/block/partitions/ldm.h b/block/partitions/ldm.h index 1ca63e97bccc..172432ce5c0f 100644 --- a/block/partitions/ldm.h +++ b/block/partitions/ldm.h @@ -93,7 +93,7 @@ struct frag { /* VBLK Fragment handling */ u8 num; /* Total number of records */ u8 rec; /* This is record number n */ u8 map; /* Which portions are in use */ - u8 data[0]; + u8 data[]; }; /* In memory LDM database structures. */ diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h index aae99a2d7bd4..a3314dd781a7 100644 --- a/drivers/block/drbd/drbd_int.h +++ b/drivers/block/drbd/drbd_int.h @@ -620,7 +620,7 @@ struct fifo_buffer { unsigned int head_index; unsigned int size; int total; /* sum of all values */ - int values[0]; + int values[]; }; extern struct fifo_buffer *fifo_alloc(unsigned int fifo_size); diff --git a/drivers/block/drbd/drbd_protocol.h b/drivers/block/drbd/drbd_protocol.h index e6fc5ad72501..dea59c92ecc1 100644 --- a/drivers/block/drbd/drbd_protocol.h +++ b/drivers/block/drbd/drbd_protocol.h @@ -271,7 +271,7 @@ struct p_rs_param { u32 resync_rate; /* Since protocol version 88 and higher. */ - char verify_alg[0]; + char verify_alg[]; } __packed; struct p_rs_param_89 { @@ -305,7 +305,7 @@ struct p_protocol { u32 two_primaries; /* Since protocol version 87 and higher. */ - char integrity_alg[0]; + char integrity_alg[]; } __packed; @@ -360,7 +360,7 @@ struct p_sizes { u16 dds_flags; /* use enum dds_flags here. */ /* optional queue_limits if (agreed_features & DRBD_FF_WSAME) */ - struct o_qlim qlim[0]; + struct o_qlim qlim[]; } __packed; struct p_state { @@ -409,7 +409,7 @@ struct p_compressed_bm { */ u8 encoding; - u8 code[0]; + u8 code[]; } __packed; struct p_delay_probe93 { diff --git a/drivers/block/rbd_types.h b/drivers/block/rbd_types.h index ac98ab6ccd3b..a600e0eb6b6f 100644 --- a/drivers/block/rbd_types.h +++ b/drivers/block/rbd_types.h @@ -93,7 +93,7 @@ struct rbd_image_header_ondisk { __le32 snap_count; __le32 reserved; __le64 snap_names_len; - struct rbd_image_snap_ondisk snaps[0]; + struct rbd_image_snap_ondisk snaps[]; } __attribute__((packed));