From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E836C636CD for ; Wed, 1 Feb 2023 17:18:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232009AbjBARSt (ORCPT ); Wed, 1 Feb 2023 12:18:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44670 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232013AbjBARSp (ORCPT ); Wed, 1 Feb 2023 12:18:45 -0500 Received: from mx01.omp.ru (mx01.omp.ru [90.154.21.10]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D4A124616F; Wed, 1 Feb 2023 09:18:42 -0800 (PST) Received: from [192.168.1.103] (178.176.77.227) 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 15.2.986.14; Wed, 1 Feb 2023 20:18:34 +0300 Subject: Re: [PATCH] ata: pata_hpt37x: fix potential forever loop From: Sergey Shtylyov To: Dan Carpenter CC: Damien Le Moal , , References: <98e8e8cb-53a3-c247-078e-85724079ecad@omp.ru> Organization: Open Mobile Platform Message-ID: Date: Wed, 1 Feb 2023 20:18:13 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <98e8e8cb-53a3-c247-078e-85724079ecad@omp.ru> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [178.176.77.227] 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: 5.9.59, Database issued on: 02/01/2023 17:00:31 X-KSE-AntiSpam-Status: KAS_STATUS_NOT_DETECTED X-KSE-AntiSpam-Method: none X-KSE-AntiSpam-Rate: 59 X-KSE-AntiSpam-Info: Lua profiles 175185 [Feb 01 2023] X-KSE-AntiSpam-Info: Version: 5.9.59.0 X-KSE-AntiSpam-Info: Envelope from: s.shtylyov@omp.ru X-KSE-AntiSpam-Info: LuaCore: 502 502 69dee8ef46717dd3cb3eeb129cb7cc8dab9e30f6 X-KSE-AntiSpam-Info: {rep_avail} X-KSE-AntiSpam-Info: {Tracking_from_domain_doesnt_match_to} 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: 178.176.77.227 in (user) b.barracudacentral.org} X-KSE-AntiSpam-Info: {Found in DNSBL: 178.176.77.227 in (user) dbl.spamhaus.org} X-KSE-AntiSpam-Info: d41d8cd98f00b204e9800998ecf8427e.com:7.1.1;omp.ru:7.1.1;127.0.0.199:7.1.2 X-KSE-AntiSpam-Info: ApMailHostAddress: 178.176.77.227 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: 02/01/2023 17:03:00 X-KSE-AttachmentFiltering-Interceptor-Info: protection disabled X-KSE-Antivirus-Interceptor-Info: scan successful X-KSE-Antivirus-Info: Clean, bases: 2/1/2023 3:09:00 PM X-KSE-BulkMessagesFiltering-Scan-Result: InTheLimit Precedence: bulk List-ID: X-Mailing-List: kernel-janitors@vger.kernel.org On 2/1/23 5:59 PM, Sergey Shtylyov wrote: [...] >> This code accidentally reuses the "tries" iterator for both the inside >> and outside loops. It could result in a forever loop if the "tries" >> variable gets reset to 0x1000 and never reaches 0x5000. Have you actually seen this happening? >> >> Fixes: 669a5db411d8 ("[libata] Add a bunch of PATA drivers.") >> Signed-off-by: Dan Carpenter >> --- >> drivers/ata/pata_hpt37x.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/ata/pata_hpt37x.c b/drivers/ata/pata_hpt37x.c >> index ce3c5eaa7e76..35be9a095b18 100644 >> --- a/drivers/ata/pata_hpt37x.c >> +++ b/drivers/ata/pata_hpt37x.c >> @@ -621,14 +621,14 @@ static int hpt37x_calibrate_dpll(struct pci_dev *dev) >> { >> u8 reg5b; >> u32 reg5c; >> - int tries; >> + int tries, tries2; >> >> for (tries = 0; tries < 0x5000; tries++) { >> udelay(50); >> pci_read_config_byte(dev, 0x5b, ®5b); >> if (reg5b & 0x80) { >> /* See if it stays set */ >> - for (tries = 0; tries < 0x1000; tries++) { >> + for (tries2 = 0; tries2 < 0x1000; tries2++) { >> pci_read_config_byte(dev, 0x5b, ®5b); >> /* Failed ? */ >> if ((reg5b & 0x80) == 0) > > Looks like Alan tried to "fix" the DPLL calibration code imported from drivers/ide/hpt366.c > and failed at that... :-) The iriginal code has 2 sequential loops (thus 'tries' could be used > for both). In principle, I agree with a simplistic patch: Err, wait! Once we have bit 7 of the PCI register at 0x5b set, we'll never return to the outer loop... So, I'm ot seeing the bug here... > Reviewed-by: Sergey Shtylyov So I have to take this back... MBR, Sergey