From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from omta038.useast.a.cloudfilter.net (omta038.useast.a.cloudfilter.net [44.202.169.37]) (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 029B61DDA30 for ; Fri, 1 Nov 2024 20:47:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=44.202.169.37 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730494030; cv=none; b=cDO+BIgma1sy0tDzaY/6m7ojp4i3ksFnD76GQ5Gb+V7WZTI9woBXI3N29eJHNpkL0860pPOr5TNFzxrSO/mKHzmWLr9Ew3MIx18bGNXXT88EE0Yxr4UiaS7lkwccm+JpXgyqsvb3L3T/DMO7VzdMwgt1S3damV/W19tcmYtKEdc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730494030; c=relaxed/simple; bh=YjrdHHWPygCe3Tc91Skobz0JFEZpvAIk6PPlQqladDw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=obBvUC52Uzkr3In8acPRLrkA90XUFY3V0hWaF9LVaUD8NZXj1Q5A8h/wqaU1MghlV4bo5qMoi0GO/lxw1qG8673edDrKAUsXwq3OIwv7UcjAhbT1Dj5EfT3kUqnJYGpK1XpJ6Um5usJEENZ1wGslMurjRJJhNF8FIbIZbBEiKNU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=embeddedor.com; spf=pass smtp.mailfrom=embeddedor.com; dkim=pass (2048-bit key) header.d=embeddedor.com header.i=@embeddedor.com header.b=za8byT+J; arc=none smtp.client-ip=44.202.169.37 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=embeddedor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=embeddedor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=embeddedor.com header.i=@embeddedor.com header.b="za8byT+J" Received: from eig-obgw-6003a.ext.cloudfilter.net ([10.0.30.151]) by cmsmtp with ESMTPS id 6uL8ttZBpg2lz6yXttvURW; Fri, 01 Nov 2024 20:47:01 +0000 Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with ESMTPS id 6yXst7ds0CgT66yXstqGjR; Fri, 01 Nov 2024 20:47:00 +0000 X-Authority-Analysis: v=2.4 cv=XvwxOkF9 c=1 sm=1 tr=0 ts=67253e44 a=1YbLdUo/zbTtOZ3uB5T3HA==:117 a=GtNDhlRIH4u8wNL3EA3KcA==:17 a=IkcTkHD0fZMA:10 a=VlfZXiiP6vEA:10 a=7T7KSl7uo7wA:10 a=VwQbUJbxAAAA:8 a=wK7pc38KeiHN8xZw7ncA:9 a=QEXdDO2ut3YA:10 a=Xt_RvD8W3m28Mn_h3AK8:22 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=embeddedor.com; s=default; h=Content-Transfer-Encoding:Content-Type: In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=xkm1nD8TrvBAERDn/msYL9E1SOOvU/GM4tbcKD0/Xvo=; b=za8byT+JHW/OuZ3qlgIE7q+J5H XM0IdHIEEaEzP9eWLq7jLmsLp0GUCflqfKs5YAkBhwB75NBoZLgVQCNNxUIz3S+vANpzqrFSzCKuy mQSXGAHZBEwPMo7B3T744Y0JgZTsCOyhxgHaHFtK2e5d6Gpmd1f/xNoIsuB7NSw0icDqLcnQBH5OM F0T7bsq6EczEWJ7A9cxd2pAtT0mrnbO9npQZrxQiUmp/T863zc4ryRCDOM6Z5JsVc4VUV6UMrEs9/ lJw5roOdcGKfJZhj8TMS1r10kOIaPLZqa1QLIHyIsIZasjEGyV7Y1/0vQPI9ELE6CRVvIlbVxs2ba 0KjimPTQ==; Received: from [177.238.21.80] (port=22208 helo=[192.168.0.27]) by gator4166.hostgator.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.96.2) (envelope-from ) id 1t6yXr-003xjs-1M; Fri, 01 Nov 2024 15:46:59 -0500 Message-ID: Date: Fri, 1 Nov 2024 14:46:56 -0600 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH][next] jbd2: Avoid dozens of -Wflex-array-member-not-at-end warnings To: Jan Kara Cc: "Gustavo A. R. Silva" , Theodore Ts'o , Jan Kara , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org References: <20241031123313.dfcuttwzzs5f5i7a@quack3> <20241031213208.gzr5jv2kg5eobjuo@quack3> <20241101101512.eee2nkaqgffsoxe3@quack3> Content-Language: en-US From: "Gustavo A. R. Silva" In-Reply-To: <20241101101512.eee2nkaqgffsoxe3@quack3> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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: 177.238.21.80 X-Source-L: No X-Exim-ID: 1t6yXr-003xjs-1M X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: ([192.168.0.27]) [177.238.21.80]:22208 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 3 X-Org: HG=hgshared;ORG=hostgator; X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes X-CMAE-Envelope: MS4xfE9sVmjLuWcqorZlYIVwlRLX2fHdIMVV3HDzDldpSIdWSvggY3cB//B5sF2n/0mo5nKPUI+Dc3OgmbwMN5fmlKxLyaUc+WjJ7/vfhIo9uBamKX2mgg65 zyT+zKnmUMwk0OeUlKff8/fOOVtM5bENEYXFPSmJMj0x9NsqBQPX4kGKkNy1IbLihMF+Pitf2OFIfnDKchMLHz8zi9cHd02PX46VkfiGF/vhpFwB+HXEcNB3 On 01/11/24 04:15, Jan Kara wrote: > On Thu 31-10-24 17:31:34, Gustavo A. R. Silva wrote: >> On 31/10/24 15:32, Jan Kara wrote: >>> >>>> `sizeof(ctx) == 4` when `char ctx[JBD_MAX_CHECKSUM_SIZE];` >>>> >>>> To maintain the same size, we tell `DEFINE_RAW_FLEX()` to allocate `1` >>>> element for the flex array, as in 32-bit `sizeof(void *) == 4`. >>> >>> So I agree we end up allocating enough space on stack but it is pretty >>> subtle and if JBD_MAX_CHECKSUM_SIZE definition changes, we have a problem. >>> I think we need something like (JBD_MAX_CHECKSUM_SIZE + sizeof(*desc->__ctx) >>> - 1) / sizeof(*desc->__ctx))? >> >> I see. Well, in that case it'd be something more like: >> >> - struct { >> - struct shash_desc shash; >> - char ctx[JBD_MAX_CHECKSUM_SIZE]; >> - } desc; >> + DEFINE_RAW_FLEX(struct shash_desc, desc, __ctx, >> + (JBD_MAX_CHECKSUM_SIZE + >> + sizeof(*((struct shash_desc *)0)->__ctx)) / >> + sizeof(*((struct shash_desc *)0)->__ctx)); >> >> Notice that `desc` is created inside `DEFINE_RAW_FLEX()` > Right. Thanks for fixing this. The cleanest option then probably is: > > DEFINE_RAW_FLEX(struct shash_desc, desc, __ctx, > DIV_ROUND_UP(JBD_MAX_CHECKSUM_SIZE, > sizeof(*((struct shash_desc *)0)->__ctx))) OK. There you go v2: https://lore.kernel.org/linux-hardening/ZyU94w0IALVhc9Jy@kspp/ Thanks a lot for the feedback. :) -- Gustavo