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Received: from BN7PR04MB4388.namprd04.prod.outlook.com (2603:10b6:406:f8::19) by BN8PR04MB6164.namprd04.prod.outlook.com (2603:10b6:408:5e::26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4867.11; Thu, 13 Jan 2022 14:39:26 +0000 Received: from BN7PR04MB4388.namprd04.prod.outlook.com ([fe80::e53a:dc46:9edd:9142]) by BN7PR04MB4388.namprd04.prod.outlook.com ([fe80::e53a:dc46:9edd:9142%7]) with mapi id 15.20.4867.012; Thu, 13 Jan 2022 14:39:26 +0000 Message-ID: Date: Thu, 13 Jan 2022 09:39:23 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.4.1 Subject: Re: [PATCH] fhandler_pipe: add sanity limit to handle loops Content-Language: en-US To: cygwin@cygwin.com References: <622d3ac6-fa5d-965c-52da-db7a4463fffd@cornell.edu> <20211225121902.54b82f1bb0d4f958d34a8bb7@nifty.ne.jp> <20211225131242.adef568db53d561a6b134612@nifty.ne.jp> <20211226021010.a2b2ad28f12df9ffb25b6584@nifty.ne.jp> <8172019c-e048-4fe2-79c9-0b3262057d3e@cornell.edu> <20220113195638.d64430e6b03159c70721fb45@nifty.ne.jp> From: Ken Brown In-Reply-To: <20220113195638.d64430e6b03159c70721fb45@nifty.ne.jp> Content-Type: text/plain; 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You can use the ReturnLength parameter of NtQueryInformationProcess to see >> how big a buffer is needed. This might be more efficient than repeatedly >> doubling the buffer size. > > Even if ReturnLength is used, the first NtQueryInformationProcess() > call and the second NtQueryInformationProcess() call will not be > done in atomic, so retrying is still necessary. However, it may be > more efficient as you mentioned. > > The similar is true also for NtQuerySystemInformation(). > > Do you still think it is better to use ReturnLength rather than > doubling the buffer? I'm not sure. I only mentioned it because I saw that that's what Process Hacker did, but still in a retry loop as you said. I suspect it doesn't make a lot of difference in practice, since we call the function once and then cache the value. Do whatever you think is best. Thanks. Ken