From patchwork Thu May 7 19:25:50 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: 11534797 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 879AA1392 for ; Thu, 7 May 2020 19:21:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 708D524953 for ; Thu, 7 May 2020 19:21:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879285; bh=LzS3WkLEkY5cS9HhYedg7dL8hIWbzOpus+g7yFKnoSg=; h=Date:From:To:Cc:Subject:List-ID:From; b=m6m99EKMc61A4lDof6JzUEPCMlY6DUCrdR1x/kGVc4dIpsNNec6jKqXbY9EFzcf8r k7s9o/kQbpqyxRxxO01SZbBvU8vL8k8Fje93CRBRXmaZkOJAxNFOaQwSPEmCNyyOGt iPr3kY/Dd/lX09Gs4LRahCCwrbkzeCvYzG2XKPp4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728743AbgEGTVZ (ORCPT ); Thu, 7 May 2020 15:21:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:42994 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728309AbgEGTVY (ORCPT ); Thu, 7 May 2020 15:21:24 -0400 Received: from embeddedor (unknown [189.207.59.248]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CB1AA208D6; Thu, 7 May 2020 19:21:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879284; bh=LzS3WkLEkY5cS9HhYedg7dL8hIWbzOpus+g7yFKnoSg=; h=Date:From:To:Cc:Subject:From; b=Kg8Ub230vZM5el8GxJinpdLe5+WYA+dyaY2jtwqzGtR5MG1v6hlsnhV4rsqkXE/Qi EXp7+48CRJneGlH0ejE09Dful5Jy8MKRyZQju0qEsyrdbUVlP+gQtQ92VYZ13Ba43q e01X+EEvPW+MnMfy44PfdsrXfxvlEod7W1fb1fcw= Date: Thu, 7 May 2020 14:25:50 -0500 From: "Gustavo A. R. Silva" To: linux-kernel@vger.kernel.org Cc: Alim Akhtar , Avri Altman , linux-scsi@vger.kernel.org Subject: [PATCH] scsi: ufs: Replace zero-length array with flexible-array Message-ID: <20200507192550.GA16683@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@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] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. 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 --- drivers/scsi/ufs/ufshcd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 698e8d20b4ba..cd34a7873623 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -3223,7 +3223,7 @@ static inline int ufshcd_read_desc(struct ufs_hba *hba, struct uc_string_id { u8 len; u8 type; - wchar_t uc[0]; + wchar_t uc[]; } __packed; /* replace non-printable or non-ASCII characters with spaces */