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charset=UTF-8 Date: Sat, 04 Apr 2026 13:37:27 +0900 Message-Id: Cc: "John Hubbard" , "Gary Guo" , "Alice Ryhl" , "David Airlie" , "Simona Vetter" , "Alistair Popple" , "Joel Fernandes" , "Timur Tabi" , "Zhi Wang" , "Eliot Courtney" , , , Subject: Re: [PATCH v4 2/2] gpu: nova-core: gsp: fix undefined behavior in command queue code From: "Alexandre Courbot" To: "Danilo Krummrich" , "Gary Guo" References: <20260401-cmdq-ub-fix-v4-0-a9a9cf982485@nvidia.com> <20260401-cmdq-ub-fix-v4-2-a9a9cf982485@nvidia.com> <11466450-aeb3-48d3-a86f-934346fd4172@nvidia.com> In-Reply-To: X-ClientProxiedBy: TYCP286CA0347.JPNP286.PROD.OUTLOOK.COM (2603:1096:405:7c::7) To CH2PR12MB3990.namprd12.prod.outlook.com (2603:10b6:610:28::18) 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: CH2PR12MB3990:EE_|SA3PR12MB9177:EE_ X-MS-Office365-Filtering-Correlation-Id: 60ce609e-992b-49fa-8bdb-08de9203e254 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|10070799003|1800799024|366016|56012099003|18002099003|22082099003; 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These regions can change without notice, >>> and thus creating a slice to them, even if never accessed, is undefined >>> behavior. >>>=20 >>> Fix this by rewriting these methods to use pointer projections in order >>> to create slices to valid regions only. It should eventually be replace= d >>> by `IoView` and `IoSlice` once they land. >>>=20 >>> Fixes: 75f6b1de8133 ("gpu: nova-core: gsp: Add GSP command queue bindin= gs and handling") >>> Reported-by: Danilo Krummrich >>> Closes: https://lore.kernel.org/all/DH47AVPEKN06.3BERUSJIB4M1R@kernel.o= rg/ >>> Reviewed-by: Gary Guo >>> Reviewed-by: Danilo Krummrich >>> Signed-off-by: Alexandre Courbot >>> --- >>> drivers/gpu/nova-core/gsp/cmdq.rs | 114 ++++++++++++++++++++++--------= -------- >>> 1 file changed, 65 insertions(+), 49 deletions(-) >> >> This is causing a build_assert failure in the latest drm-rust-next, with >> rustc 1.85.0, and also with 1.78.0. >> >> rustc 1.93.0 does not show the problem. > > Odd, it did pass all the testing at my end. Anyways, it only proves once = again > that this is pretty fragile. Same here, although I did not test with all the supported rustc versions (but pretty sure I did test 1.78). This seems to be heavily configuration dependent. Gary, do you know of a way to restrict the `project_pointer` macro to only take constant values as indices? That problem is pretty sneaky and likely to happen again, so we should probably harden that part a bit.