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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 17131CAC592 for ; Fri, 19 Sep 2025 16:40:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=GDz0HUmxQMj6JfUxaJgfV0Ve2eC/UQxPjQKEq7AEPeQ=; b=TOUVlkIKti0vK22fc8WZxrtL0J o+7R2jcD/oxUYvI9nGhp1gG3ezpjyxBFChZSoMq9AcAkwiQK6ut1gH9Ci5kS5Z8jql+szcqyNryoC f24g+kFO7Q1Mxwe9pOMjjsfrlD0b+JuXPH6+Ts8orp5QJH0B6F4FJt1kqz9xRSy9OGzVGog0WHYxP 01r6g6ebXZ9ZXHKGhuIKVbwHuET0n+dnnV8SFVL4iwfgnIbWJgfnukVygEHmk6iBPQLqvxiQUbLOA 8GyYfGwyJE7bqdDrrZimBDYzYbXFwkP9mMJtMHMwiIjjdVJOuDAvnA+kERRMJeWsRk6eWKAe2bElR xnGV43ZQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uze9W-00000003YPP-428b; Fri, 19 Sep 2025 16:40:06 +0000 Received: from mail-wr1-x432.google.com ([2a00:1450:4864:20::432]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uze9U-00000003YOV-2g8j for linux-arm-kernel@lists.infradead.org; Fri, 19 Sep 2025 16:40:05 +0000 Received: by mail-wr1-x432.google.com with SMTP id ffacd0b85a97d-3ee12332f3dso1983762f8f.2 for ; Fri, 19 Sep 2025 09:40:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1758300003; x=1758904803; darn=lists.infradead.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=GDz0HUmxQMj6JfUxaJgfV0Ve2eC/UQxPjQKEq7AEPeQ=; b=nBwQ6gpaonwlPqK7AvESjznOhIlTVIjWoUcKWP0ftkZX0bKmmN3YR88YOCq4mGbD3r aVKFe7RioAFxdqA3SBjz8bNNM+QcgJCBcZA5zdeLal75hO9reTZ4eyWJJFceJJI9fRr+ 8oA228CecrFTCaMCSqUCXYb4+pzcygPVR8bB0G5XqulE2gaE6KBodktzPS3HfBeaRtam +VksylvYzPUu0bUv69gdDxBcI9XACYHpfcz3jx5u3t46l7V5QcCJMN4teBknphLmOmnJ 8Z7rkNYvkX1NAs4+rWNLid/TuhGSnDNc2CU5KvjMJcoaeQEVfvy5Q3QqlAnsyzVMuBPA QMhg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1758300003; x=1758904803; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=GDz0HUmxQMj6JfUxaJgfV0Ve2eC/UQxPjQKEq7AEPeQ=; b=JugS/44O2i52rudTIq4Ac7obozKG1G9epIQBKRV4vqBn8XJyjVY8Stv/lFxPexu7yA rZNj9uNthGpwAeQALsyAT20pH5Xj1H3GOqU7A2YC+YF5YRjlM2w4jg4KQr694ON26Jlk oiInKzo+o4cJGIc8VXyE/tI6v5bz/tITnqi9gNmV9kIoEi0+PABc22OxRuigBS548KOI CC1h56daQLppks4m4vsvxpnZxCaUlR10w4lKgi6/eO8rjuOi+XOhxTq1/1IIwCvFV2qw fnizEhwRVuAL3O8Wwbo7bwjt099jEZnN1gwaMc7IY7fMMhxAeROnJfiCtdYIQGXALeba VIFA== X-Gm-Message-State: AOJu0YxBJUj1Io70+Q7hCOEbqpIwHnDzKqc/STGMSLC6FN8YEj+xH4i2 k424VQ3yKdX5iGF7fbA+aFxeXwcV96MqvXWGiUp6QAOcx8e35R7qS9gy8zSSadfT7Q== X-Gm-Gg: ASbGncv6MIx9hkw519WfIfVwTb5y6iJM5hWFNCuyqPD/DEWboEnlsOaGXOXWuPAVGQm qVUXcsLP7O7pGkcHsWsvH3A8fIgzXulvl5zFchQuJRQrddCVMXY5Y0KZEfIr6pAW0Ab2uA7n4eK 0oSS1COIRJoH7CqlKYKfZpb616NXX2OC1ucLMxfqKF1eV2I3jh2T6/LvScrAJdEtpBJxJNGmW08 0VK+h7ROLUcymrvyJ+O+FjwcAUffaUjoPO13/LLMuzAftQ1KJRt1zqAaUvVS+G1XWnRjohSVylT 1/HEy8E965rNHcWOJtU7C1cmJaYmz7ZnZqf9BF0jy00KGSfN7GSPnsQmPI+XjKM1lEYCXDtGoID rdITeEBfDD6HhVUz4FNWGWJVO1AWQYmDiWxfaAU8VWrV8RBd5M2YM06L5 X-Google-Smtp-Source: AGHT+IGu6mx9xF/KpgWa+Ws5nc8mB0EaI0MQ70JJE8g45ggZtRlbBaKCVGwil9FkQGJGfwXu4YDS2w== X-Received: by 2002:a05:6000:605:b0:3e7:5f26:f1ea with SMTP id ffacd0b85a97d-3ee7e0116c9mr3218272f8f.20.1758300002660; Fri, 19 Sep 2025 09:40:02 -0700 (PDT) Received: from google.com (32.134.38.34.bc.googleusercontent.com. [34.38.134.32]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3ee0fbc7478sm8458140f8f.38.2025.09.19.09.40.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Sep 2025 09:40:01 -0700 (PDT) Date: Fri, 19 Sep 2025 16:39:59 +0000 From: Adrian =?utf-8?Q?Barna=C5=9B?= To: Ard Biesheuvel Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , Dylan Hatch , Mark Rutland , Fanqin Cui Subject: Re: [PATCH 2/2] arch: arm64: Reject modules with internal alternative callbacks Message-ID: References: <20250919122321.946462-1-abarnas@google.com> <20250919122321.946462-3-abarnas@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250919_094004_698121_D7CD8975 X-CRM114-Status: GOOD ( 16.15 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Sep 19, 2025 at 05:01:09PM +0200, Ard Biesheuvel wrote: >Hi Adrian, > >On Fri, 19 Sept 2025 at 14:23, Adrian Barnaś wrote: >> >> During module loading, check if there is a callback function used by the >> alternatives specified in the '.altinstruction' ELF section and block >> loading the module if such a function is present. >> > >Why? > >AIUI, the issue being addressed is the fact that we cannot yet execute >code from the module itself when alternatives are being applied, and >so the callback must live in the core kernel, or in another module. > >So this is a really big hammer, given that it disallows all callback >alternatives, including ones that we could easily support. Yes, it is true. What about we check if cb resides in kernel .text using core_kernel_text()? Pointer should be valid already since applying alternatives is done after relocation. We can shrink the hammer a bit. Then we allow the callback from inside the kernel to be called from the module but reject modules with callbacks that are invalid. Thanks, Adrian