From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx01.omp.ru (mx01.omp.ru [90.154.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 85181F9E8; Tue, 16 Jul 2024 15:41:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.154.21.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721144525; cv=none; b=Hsdl1kfeK2AbfUuMtaRntN3ULHikF/RVGjTRhFSqnXfFtguMRXa4sw+5qxFMxsJBcifmzf6YHhPRZokZyoch30CEIgw11cWst506jRizUnSUstsE2EDMT2IsIOhJMOAEuHTmnRgbOGcoAFgjvBRWQgJDV5a/EmlpRmY78R7C7IA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721144525; c=relaxed/simple; bh=zBoXikfS0DYHkE7nQK2Clg9f1dRTsl9vE7fWg7VizRE=; h=Subject:To:CC:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=ZkqWUuRn1zMUf2MvvliXcR+uJBZsjkx9WBg/tjcs2cUEpET1v8HDuFTThSB7kL5RQWjLv2x/MJbuiJBEDD7252B+Emv53s5zjVu888+VpX35bVRGFiVHXUfHxi3RbS91gDi7MYsYu9Gr1k+OhWpqMWx/Knff9MtOpfe7xzECiI8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=omp.ru; spf=pass smtp.mailfrom=omp.ru; arc=none smtp.client-ip=90.154.21.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=omp.ru Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=omp.ru Received: from [192.168.1.105] (178.176.73.18) by msexch01.omp.ru (10.188.4.12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.1258.12; Tue, 16 Jul 2024 18:41:49 +0300 Subject: Re: [PATCH] fs: buffer: set the expression type to unsigned long in folio_create_buffers() To: Roman Smirnov , Alexander Viro , Christian Brauner , Jan Kara CC: , , References: <20240716090105.72179-1-r.smirnov@omp.ru> From: Sergey Shtylyov Organization: Open Mobile Platform Message-ID: <5002a830-6a66-82fc-19e3-ec1e907eeb49@omp.ru> Date: Tue, 16 Jul 2024 18:41:49 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20240716090105.72179-1-r.smirnov@omp.ru> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: msexch01.omp.ru (10.188.4.12) To msexch01.omp.ru (10.188.4.12) X-KSE-ServerInfo: msexch01.omp.ru, 9 X-KSE-AntiSpam-Interceptor-Info: scan successful X-KSE-AntiSpam-Version: 6.1.0, Database issued on: 07/16/2024 15:17:05 X-KSE-AntiSpam-Status: KAS_STATUS_NOT_DETECTED X-KSE-AntiSpam-Method: none X-KSE-AntiSpam-Rate: 59 X-KSE-AntiSpam-Info: Lua profiles 186542 [Jul 16 2024] X-KSE-AntiSpam-Info: Version: 6.1.0.4 X-KSE-AntiSpam-Info: Envelope from: s.shtylyov@omp.ru X-KSE-AntiSpam-Info: LuaCore: 24 0.3.24 186c4d603b899ccfd4883d230c53f273b80e467f X-KSE-AntiSpam-Info: {rep_avail} X-KSE-AntiSpam-Info: {relay has no DNS name} X-KSE-AntiSpam-Info: {SMTP from is not routable} X-KSE-AntiSpam-Info: {Found in DNSBL: 178.176.73.18 in (user) b.barracudacentral.org} X-KSE-AntiSpam-Info: {Found in DNSBL: 178.176.73.18 in (user) dbl.spamhaus.org} X-KSE-AntiSpam-Info: 127.0.0.199:7.1.2;178.176.73.18:7.1.2;omp.ru:7.1.1;d41d8cd98f00b204e9800998ecf8427e.com:7.1.1 X-KSE-AntiSpam-Info: ApMailHostAddress: 178.176.73.18 X-KSE-AntiSpam-Info: {DNS response errors} X-KSE-AntiSpam-Info: Rate: 59 X-KSE-AntiSpam-Info: Status: not_detected X-KSE-AntiSpam-Info: Method: none X-KSE-AntiSpam-Info: Auth:dmarc=temperror header.from=omp.ru;spf=temperror smtp.mailfrom=omp.ru;dkim=none X-KSE-Antiphishing-Info: Clean X-KSE-Antiphishing-ScanningType: Heuristic X-KSE-Antiphishing-Method: None X-KSE-Antiphishing-Bases: 07/16/2024 15:19:00 X-KSE-Antivirus-Interceptor-Info: scan successful X-KSE-Antivirus-Info: Clean, bases: 7/16/2024 12:52:00 PM X-KSE-Attachment-Filter-Triggered-Rules: Clean X-KSE-Attachment-Filter-Triggered-Filters: Clean X-KSE-BulkMessagesFiltering-Scan-Result: InTheLimit On 7/16/24 12:01 PM, Roman Smirnov wrote: > Shift without specifying the type casts the expression to int, You mean the result of the shift? Or what expression? > which is then passed as an unsigned long argument. It is necessary And here we'll have at least one potential problem (that you neglected to describe): with 1 << 31, that 1 will land in a sign bit and then, when it's implicitly cast to *unsigned long*, the 32-bit value will be sign- extended to 64-bit on 64-bit arches) and then we'll have an incorrect size (0xffffffff80000000) passed to create_empty_buffers()... > to use 1UL instead. Perphas was worth noting that using 1UL saves us 1 movsx instruction on x86_64... > Found by Linux Verification Center (linuxtesting.org) with Svace. > > Signed-off-by: Roman Smirnov [...] MBR, Sergey