From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from LO0P265CU003.outbound.protection.outlook.com (mail-uksouthazon11022078.outbound.protection.outlook.com [52.101.96.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 176104915BF; Thu, 8 Oct 2026 12:24:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.96.78 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791462278; cv=fail; b=K4KWBMYB41GMyMtve+lnafI2PDSmWG1QTOpXGuA10383BVh/0QrXnSY7EQIRlRXx8blsgf8lNVdyCemMgUhqcqlbVj71wtTg5vg5l/SIKWuxUhbrRLOq+3AQTzRaZ/+6BYKeS01a/DbqEzfQSFgWjw4XXNgsxqCV4zvx+CJIfs4= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791462278; c=relaxed/simple; bh=xdmtw7FgwAOO3NBHYo6F4EoVPDCt0zinnHs5twXfVuY=; h=From:Date:Subject:Content-Type:Message-Id:References:In-Reply-To: To:Cc:MIME-Version; b=j0r5biWgxWSA5ihdlqc4Lt9XYosCPmhkDqypcMSo25vNnXozBxCokQafwqjA0jBAtCO4efah8uJlIPRTJpkOJCd1SBb5aUmL6nOrE05dXzeKcwxjz8CPfLNxf3LbNpBg20KpfLJsr0UhyNcgNmvS6jql9XsiIB7WAzxexhmdqEs= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=garyguo.net; spf=pass smtp.mailfrom=garyguo.net; dkim=pass (1024-bit key) header.d=garyguo.net header.i=@garyguo.net header.b=Ny0a7UOK; arc=fail smtp.client-ip=52.101.96.78 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=garyguo.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=garyguo.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=garyguo.net header.i=@garyguo.net header.b="Ny0a7UOK" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=SgQEks+QDWhPUzuO+XNCrdmnV9FIOiLGFC64s5l6hke5TxJlOM8bwz3Fi4xTevFXnDETkg7Iwe2xvYVCcEV1ReWBU0Fms4MDckH0lhgQlaLLXknk2M20QIFzpjwjbDUFdhNJ38XMmb33D8TmzfsrLSX3mPFpJlMeombIsIwUE55/zk6cKX2AbDsw0QxmJsU9O/39Nre9EIIpC9q92tJJ7mqnHELxlB9x7bpIizrWrgU3z9MSwZ9MXp1ZaQEzVPe/M64PdWk3PRj+jQYg5xMCJ63+lBbFRBDRR9f5sxMxRgTq1f+8lVL5WgbJDQAT3RLreC+ZY9XZM9xnvBn9NDYNyA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=E/c5r4d4XeTP8eVlWP6xgOsSuAKeDQfKikEqlsehFDA=; b=WXfpU+FIm5hI6BfnyeZKmPQgMBea4PVohjmzvGxxVycXud1mYuBP+hF396VkTWrg/oDvtaMkedNQNf1BsEDK+tKiA5dN3W74XA7MsPYFy/RKq0xO91N1Vceh7we8KVSQPHYNSvpQZ5Jd3vRYHoHX3vBDccfsuG9bd0wiqWgLkXCpff4ruEbLlF5d8CdiRb/19SEM/OnN36lsf4/fPmYhA68rA0sgH1bYRmOsJ+K/hMVzRG1F2aq0gSEAtUr/dhnFbQJ4VTgyMxmDspHfFImZluDDXP7pJCi4oW3516iJiIfbtAx5p1mYRbZ0S7kjxGKeJ1lNpnCzb8gzqe0JA38dVw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=garyguo.net; dmarc=pass action=none header.from=garyguo.net; dkim=pass header.d=garyguo.net; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=garyguo.net; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=E/c5r4d4XeTP8eVlWP6xgOsSuAKeDQfKikEqlsehFDA=; b=Ny0a7UOKNLUxc44CHaGo++v2x0Z+hj3cRzL/puN6RiVJsDI1UXiN0zG/PVuX0Ahzy226eDnYDUlNc3yv5yYizA4IOkhqhgxJGH2/tGua5Oa0+RvtU33Zpck6YeojFKojuen1doOkV/zbA8Dx5f71y/Rw1fs7jCHWuo2w87WjhsY= Authentication-Results: mx.microsoft.com 1; dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=garyguo.net; Received: from LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:4ab::19) by LO2P265MB5471.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:25e::9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.496.17; Thu, 8 Oct 2026 12:24:31 +0000 Received: from LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM ([fe80::f60b:1537:68d7:4fc1]) by LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM ([fe80::f60b:1537:68d7:4fc1%6]) with mapi id 15.21.0496.015; Thu, 8 Oct 2026 12:24:31 +0000 From: Gary Guo Date: Thu, 08 Oct 2026 14:23:54 +0200 Subject: [PATCH 07/20] rust: pin-init: internal: pin_data: check covariance of self-referential fields Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261008-dev-selfref-v1-7-6c1eb269fe57@garyguo.net> References: <20261008-dev-selfref-v1-0-6c1eb269fe57@garyguo.net> In-Reply-To: <20261008-dev-selfref-v1-0-6c1eb269fe57@garyguo.net> To: Benno Lossin , Miguel Ojeda , Boqun Feng , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , =?utf-8?q?Onur_=C3=96zkan?= Cc: linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Gary Guo X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=5414; i=gary@garyguo.net; h=from:subject:message-id; bh=xdmtw7FgwAOO3NBHYo6F4EoVPDCt0zinnHs5twXfVuY=; b=owJ4nJvAy8zAJca/kLG6/oLwNsbTakkMWce7025N7VOeYxiptOjZz35rUTvN44VLpBZ0drC93 XvdrnRC9cOOUhYGMS4GWTFFFo9uxrRNjLNlL2uVv4SZw8oEMoSBi1MAJrI8mOF/MAv7sytdK+wz 3+5QEWXWX22j8JfTXOBi4/ppHoUGsve5GRlWMFsd5hRq7mj90/ubR55lSnOu3LWf4s8iFPb+/XD ySigjAKq3RSY= X-Developer-Key: i=gary@garyguo.net; a=openpgp; fpr=E25A77AED6FDB55D05B304A09D8C6F14E3E60652 X-ClientProxiedBy: LO4P123CA0578.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:276::8) To LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:4ab::19) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LOAP265MB8560:EE_|LO2P265MB5471:EE_ X-MS-Office365-Filtering-Correlation-Id: e2f6f16d-ace0-4266-8606-08df25371ace X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|23010399003|1800799024|376014|7416014|921020|6133799003|10067099003|56012099006|22082099003|18002099003|3023799007; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM;PTR:;CAT:NONE;SFS:(13230040)(366016)(23010399003)(1800799024)(376014)(7416014)(921020)(6133799003)(10067099003)(56012099006)(22082099003)(18002099003)(3023799007);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?aHhiSmRkQ0ozZmt4NFZMZVR4UU00YXNQUkgyWUcxaGhoRkFzYWc3UnVCZFlk?= =?utf-8?B?S1VMSmh2bXBaYXJuakVnZ1B2Q0ZYK3ozSFNmNC9WWDh2Z2ZmbHk3VURXUmha?= =?utf-8?B?VkcwY2psSzA4SGozRElRYVpTaXUzU0xvSm9WNEZyQzdrT3lLRnlzN21kZ0py?= =?utf-8?B?NjlRVXVESTNlS2diWkp4M0NCZmN0RUhGK21aZzhhNUlRTXdlUHpmZDRoa04z?= =?utf-8?B?MFp4VzEzUkRVLzNEbzdoOXR0Vm1mRTBzZ0x0L2lVT2RSZ0F1eS82bWxCVjhi?= =?utf-8?B?c2Iyb0dXVXJxblJYQkxNbEw4R1hHaVQ0dnNKQ1JQV2VYc0tRVitkOCtJQ0ha?= =?utf-8?B?R253UFlQanhXRzZTVERaTkFaRElHQTI4MEpCSU5vcnVZOVd4dXlLREV3NUxM?= =?utf-8?B?UklsNFE5Q3cxMHY3Znk0cnpFL2xab0ViRTl1RWFFRFBLdEgrTXZoeU4yT1Q3?= =?utf-8?B?ditRSDVXb095eDRhcnRqOXk5blJzN0VRSWpDUEYvZ3RuVHFUaWNPdVZzNkMr?= =?utf-8?B?cEkvLzdzMm55UWt1bTE1UjBFN1JEc1d0U2doL3NJaG9KN3JiTGtSVDJWQUtZ?= =?utf-8?B?b2ZsZFVNRldXL0N0R0FwSHllSzJIL2VPMVZtVWViK0lyYWdnTGJrejNlN1FO?= =?utf-8?B?U2tQeThBSkNyUlhoVEZqMTdPWHJ2dkFFZkJZc2RCb3VZVDlORUo0MXRwZFhI?= =?utf-8?B?dEgzQk9KN3g5YkVxWGJEODJucVRmc1ZteHFCM2l6MXZQcUhOL3A2MW5hbkE1?= =?utf-8?B?UDEzODc3OHFXbjlsM2pVbkdjTi9yZlZxbTViSnprUVo3QTZZVUgvcEVOM0py?= =?utf-8?B?M2RhOW1lcTI2U09mcU0wd2dEeXdvaWJiM1pvd0gvL2VWeXZKWU5MTWlRZU1W?= =?utf-8?B?UUNtTFRpWDhNOGFJZkJxK24vL1gxMnZLd1BIZTJBV2pLeHlxdHNnbEc5WDJq?= =?utf-8?B?Z3FMYUQxaGZSbmJmQTJoQVZST0loMUdXMkNqUEJFRWRkWE5nK0VYek0rUEtV?= =?utf-8?B?TGt0UzNqaWNYKzVyYUpiWEZ3dFlHNnB3VGFmcVBZMk9ROS90SXBwZ0JJMGJ0?= =?utf-8?B?L2E1U0p6S0J1UzdHMEVoUCtWMnRUMm55em9vSEU4TElEc2Z4azgrWjVQTFhS?= =?utf-8?B?L0ZtUzZrLzdySmpQMjRaSHpiWkRibjJldGY3R2tjSC9WSW16NGdTUURzLzBl?= =?utf-8?B?MWIyUmV5d2U2YTZCL055WDU4YzgxZzFtQTNJSEk3VGVOdDNoajlhSUhCMWtn?= =?utf-8?B?d0p5cjljdERKS3ZJekdmM0JyK0pJbmRwOUsyd0JIQytyWUJMaDdFNTJya1JN?= =?utf-8?B?TmQxYVNGRWt0QUplR1FqSTZyUlU0clVpN25vVHM4MDFQNXJQM3JIMGZtV29r?= =?utf-8?B?U3lxOURnSG8vKzlwbHlxaFVQbUZpd003c2dUUThFeldSWVV1Y1lLZjYwdnYy?= =?utf-8?B?Z1Z0Tm9mTk96a09TcCtCQ2xnYllOTTNhNDd3empWMXdVUGNRaFR4N3hLdmhC?= =?utf-8?B?SWYwc3VUcEhPbnpMTkN5N1l3T3psQ2JqNVcySnBsMzE3RDFYdXNFZCtzOG5t?= =?utf-8?B?RGlGaWZvZk9yQS91ZzlSVys4aHhvN2xuU0NFUk11TTNGMmxhMWt6ellleTMv?= =?utf-8?B?WmhxTEtkMG5pbGMrTmpBc3dZQUxWd1lZVG5CQnJ0WFhtNXVnNHFsNWdKUmt1?= =?utf-8?B?SS9pcEZUSWpsQVNjeTkvNVprMXk5MXJrc0pIS2JoRkd2L2RpaitLUnZUZU41?= =?utf-8?B?OTF0ZStzQmtxT1BPeU5GMVhWSWFLeEVPVlhvVFNnNTMwSkVzT1BrVnFyeVkr?= =?utf-8?B?NU9ycmw1ZE9tODFid3haL2VHdXFLYjdDS2pHUUt6SHJ0M0R3UnJGRlJpSWg5?= =?utf-8?B?R2RzYjQzTnJzZGpFZ0hSVUNSNndHMHFoeS8ycUVBRExWUDJQL0dXeUtXQVI0?= =?utf-8?B?SExBVnc5YTFSa3FVUm5jcEdjcXdrMldwNnQ2ZWFyRTJVNld1b0N0QjJTS1JE?= =?utf-8?B?eFUrRTVHTVhSRURpQ0dFNkVqb1dPNlk2TFdEZnA0anBQL2ZWMlF1TVJlQmlP?= =?utf-8?B?emxRdWdjWTdXUVRROWIxSngvdlFHRkZFODl2cGF1SFNpSEpwdkhLc2h1K3Nk?= =?utf-8?B?YWJtcllXcmllVi9VTVp0WmN0eHRheFB0ZG5sSkhyV1hmVHBiRUduNUFUTHhI?= =?utf-8?B?VzJqemI5SXdreFQySUR5MVphcktRbElINXhoRS9VK3VsYWdYZ3FibFRPVlNI?= =?utf-8?B?Uk8wbVdrSjRKUldhckFMMnhCcXJsS3VSN0IyNFYzSUtpaG1RK2FSMTkvaHM3?= =?utf-8?B?VVdrVFRoMnIvWHFUNTNrdUhkQzB2RnU3NWZwYlJYM3N6OFY0T3VnQT09?= X-OriginatorOrg: garyguo.net X-MS-Exchange-CrossTenant-Network-Message-Id: e2f6f16d-ace0-4266-8606-08df25371ace X-MS-Exchange-CrossTenant-AuthSource: LOAP265MB8560.GBRP265.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Oct 2026 12:24:31.3989 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: bbc898ad-b10f-4e10-8552-d9377b823d45 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 34UwwnMLEG4DtjlWtXzqw6vzspM/j4YRppaDCWkjQ311XQeAWc0WaONE+7bJ0R43WoxhyYQFYpZnkcOALSiaMA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: LO2P265MB5471 We implicitly infer covariance for fields that self-references. This needs to be checked to ensure that the fields are really covariant, so the rest of expansion code can rely on this fact. Signed-off-by: Gary Guo --- rust/pin-init/internal/src/pin_data.rs | 74 +++++++++++++++++++++++++++++++++- rust/pin-init/internal/src/util.rs | 24 ++++++++++- 2 files changed, 95 insertions(+), 3 deletions(-) diff --git a/rust/pin-init/internal/src/pin_data.rs b/rust/pin-init/internal/src/pin_data.rs index 8a7a4f6d230a..0b2ac2ca856a 100644 --- a/rust/pin-init/internal/src/pin_data.rs +++ b/rust/pin-init/internal/src/pin_data.rs @@ -76,7 +76,6 @@ enum Variance { } /// Information about field lifetimes captured in a type. -#[expect(unused)] struct Capture { variance: Variance, /// Lifetime to be captured. @@ -435,6 +434,7 @@ fn expand( let unpin_impl = generate_unpin_impl(&info); let drop_impl = generate_drop_impl(&info); let drop_order_check = generate_drop_order_check(dcx, &info); + let variance_check = generate_variance_check(&info); let projections = generate_projections(&info); let the_pin_data = generate_the_pin_data(&info); @@ -444,6 +444,7 @@ fn expand( // outside. const _: () = { #drop_order_check + #variance_check #projections #the_pin_data #unpin_impl @@ -770,6 +771,77 @@ fn __drop_order_check #impl_generics_with_field_lt ( } } +/// Produce variance checks, so we can ensure that the variance of lifetimes captured by field types +/// actually match our expectation. +fn generate_variance_check(info: &StructInfo) -> TokenStream { + if !info.self_referential { + return quote!(); + } + + let mut checks = Vec::new(); + + for f in info.fields.iter() { + let covariant_captures: Vec<_> = f + .captures + .iter() + .filter(|b| b.variance == Variance::Covariant) + .map(|b| &b.lifetime) + .collect(); + if covariant_captures.is_empty() { + continue; + } + + let ident = f.member.as_ident(); + // Use the span of type for better error message. + let span = f.field.ty.span().resolved_at(Span::mixed_site()); + + let other_field_lifetimes = Generics { + lt_token: None, + params: f + .captures + .iter() + .filter(|b| b.variance != Variance::Covariant) + .map(|b| GenericParam::Lifetime(LifetimeParam::new(b.lifetime.clone()))) + .collect(), + gt_token: None, + where_clause: None, + }; + + let long = Lifetime::new("'__long", span); + let long_ty = f + .field + .ty + .replace_lifetimes(&covariant_captures, &vec![&long; covariant_captures.len()]); + + let short = Lifetime::new("'__short", span); + let short_ty = f + .field + .ty + .replace_lifetimes(&covariant_captures, &vec![&short; covariant_captures.len()]); + + let check_name = format_ident!("__{ident}_covariance", span = span); + + // Add `<'__long: '__short, 'short>` as additional generics. + let covariance_check_generics = parse_quote!(<#long: #short, #short>); + let combined_generics = CombinedGenerics(vec![ + &covariance_check_generics, + &other_field_lifetimes, + &info.struct_.generics, + ]); + + checks.push(quote_spanned!(span => + // Emit a check to ensure the type is *really* covariant for soundness. + fn #check_name #combined_generics (long: #long_ty) -> #short_ty { + long + } + )); + } + + quote!( + #(#checks)* + ) +} + fn generate_projections(info: &StructInfo) -> TokenStream { let ItemStruct { vis, diff --git a/rust/pin-init/internal/src/util.rs b/rust/pin-init/internal/src/util.rs index 3dc72e162e1e..9f5dddbde9ef 100644 --- a/rust/pin-init/internal/src/util.rs +++ b/rust/pin-init/internal/src/util.rs @@ -5,8 +5,8 @@ use proc_macro2::{Ident, TokenStream}; use quote::{format_ident, ToTokens}; use syn::{ - visit::Visit, Attribute, BoundLifetimes, GenericParam, Generics, Index, Lifetime, Member, - Token, TypePath, + parse_quote, visit::Visit, Attribute, BoundLifetimes, GenericParam, Generics, Index, Lifetime, + Member, Token, Type, TypePath, }; use crate::DiagCtxt; @@ -385,3 +385,23 @@ fn visit_type_path(&mut self, ty: &'a TypePath) { TypeParamVisitor(f) } } + +pub(crate) trait TypeExt { + fn replace_lifetimes(&self, needle: &[&Lifetime], replacement: &[&Lifetime]) -> Type; +} + +impl TypeExt for Type { + fn replace_lifetimes(&self, needle: &[&Lifetime], replacement: &[&Lifetime]) -> Type { + if needle.is_empty() { + return self.clone(); + } + + parse_quote!( + < + for<#(#needle,)*> fn(#(&#needle (),)*) -> #self + as + ::pin_init::__internal::FnOutput<(#(&#replacement (),)*)> + >::Output + ) + } +} -- 2.54.0