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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A53CC4332F for ; Mon, 13 Nov 2023 19:18:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232108AbjKMTSj (ORCPT ); Mon, 13 Nov 2023 14:18:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232031AbjKMTSW (ORCPT ); Mon, 13 Nov 2023 14:18:22 -0500 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CDAEF1BE1; Mon, 13 Nov 2023 11:17:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=SMqd4EqjIcBWaNJEJy3kwHzwVKqwQ0bk4Awnjz3pJgY=; b=lVt4SgLr063TeN8XyblCcp4C0i OeBGqN0AScamXEG5FlRkrb4uHFcaZfguSGkgXkVYxxlhdj5j8cPjWbPXjIdGStGwTNO3jmFLdyEVa mzTlBshUCglfjrfzOjPJ6XJpwj3+D7eNBT3r2AVfL87Dv756dYcYzW4rXDDVcGRdd9am+bYdx9DJx pirfn0BmJdAH6qaxfwYkdkbqLTdJMbfjz6odx8+ngbkG/WeSwT0xaF++KkWZnXll+cJ2gL+5Vb4tU QBVAj0MlIuyoK/jNBNF0QgZlVdj32fRbhathNAhoNcKfnmRF5wuT0LN84hazXm4cFVu5j153D3hAa qcIfOVJw==; Received: from 189-68-155-43.dsl.telesp.net.br ([189.68.155.43] helo=[192.168.1.60]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1r2cR2-002qRU-OW; Mon, 13 Nov 2023 20:17:25 +0100 Message-ID: Date: Mon, 13 Nov 2023 16:17:11 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.0 Subject: Re: [RFC PATCH 0/2] Introduce a way to expose the interpreted file with binfmt_misc Content-Language: en-US To: "Eric W. Biederman" , sonicadvance1@gmail.com Cc: Kees Cook , David Hildenbrand , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, kernel-dev@igalia.com, kernel@gpiccoli.net, oleg@redhat.com, yzaikin@google.com, mcgrof@kernel.org, akpm@linux-foundation.org, brauner@kernel.org, viro@zeniv.linux.org.uk, willy@infradead.org, dave@stgolabs.net, joshua@froggi.es References: <20230907204256.3700336-1-gpiccoli@igalia.com> <202310091034.4F58841@keescook> <8dc5069f-5642-cc5b-60e0-0ed3789c780b@igalia.com> <871qctwlpx.fsf@email.froward.int.ebiederm.org> From: "Guilherme G. Piccoli" In-Reply-To: <871qctwlpx.fsf@email.froward.int.ebiederm.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/11/2023 15:29, Eric W. Biederman wrote: > [...] > Currently there is a mechanism in the kernel for changing > /proc/self/exe. Would that be reasonable to use in this case? > > It came from the checkpoint/restart work, but given that it is already > implemented it seems like the path of least resistance to get your > binfmt_misc that wants to look like binfmt_elf to use that mechanism. > > Eric > Thanks Eric! I'm curious on how that would work: we'd change the symlink of the emulator? So, the *emulated* software, when reading that, would see the correct symlink? Also, just to fully clarify: are you suggesting we hook the new binfmt_misc flag proposed here to the internal kernel way of changing the proc/self/exe symlink, or are you suggesting we use the prctl() tune from the emulator, like the userspace changing its own symlink? One of the biggest concerns I have with this kind of approach is that changing the symlink actually...changes it - the binary mapping itself, I mean. Whereas my way was a "fake" change, just expose one thing for the emulated app, but changes nothing else... Cheers, Guilherme