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charset=UTF-8 Date: Thu, 08 Oct 2026 22:15:49 +0900 Message-Id: Cc: "Miguel Ojeda" , "Boqun Feng" , "Gary Guo" , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , "Benno Lossin" , "Andreas Hindborg" , "Alice Ryhl" , "Trevor Gross" , "Danilo Krummrich" , "Daniel Almeida" , "Tamir Duberstein" , =?utf-8?q?Onur_=C3=96zkan?= , "Greg Kroah-Hartman" , "Timur Tabi" , "Alistair Popple" , , Subject: Re: [PATCH] rust: uaccess: avoid unsafe unwrap_unchecked() in strcpy_into_buf() From: "Alexandre Courbot" To: "Thorsten Blum" References: <20261008061326.177841-2-blum@kernel.org> In-Reply-To: <20261008061326.177841-2-blum@kernel.org> X-ClientProxiedBy: TYWPR01CA0038.jpnprd01.prod.outlook.com (2603:1096:400:17f::8) To MW4PR12MB6873.namprd12.prod.outlook.com (2603:10b6:303:20c::17) Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MW4PR12MB6873:EE_|DS8PR12MB899436:EE_ X-MS-Office365-Filtering-Correlation-Id: bc0ed6c1-aa61-4ff2-0cf7-08df253e474a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|23010399003|7416014|376014|10070799003|366016|10067099003|11063799006|56012099006|6133799003|18002099003|22082099003; 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In this cas= e, we add a NUL-terminator > // and return it. Unlike the `len < dst.len()` branch, don't= modify `len` because it > // already represents the length including the NUL-terminato= r. > - // > - // SAFETY: Due to the check at the beginning, the buffer is = not empty. > - unsafe { *buf.last_mut().unwrap_unchecked() =3D 0 }; > + *buf.last_mut().ok_or(EINVAL)? =3D 0; I am not sure this gives us much - we are trading an unsafe statement that is well-controlled (enforced by the first two lines of the method) for a runtime check. I'd say this is working as intended here.