From nobody Tue Dec 16 16:37:38 2025 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 9B785C352A1 for ; Tue, 6 Dec 2022 15:24:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234809AbiLFPY0 (ORCPT ); Tue, 6 Dec 2022 10:24:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49474 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234621AbiLFPYJ (ORCPT ); Tue, 6 Dec 2022 10:24:09 -0500 Received: from mail-pl1-x62d.google.com (mail-pl1-x62d.google.com [IPv6:2607:f8b0:4864:20::62d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23E2910AF for ; Tue, 6 Dec 2022 07:24:07 -0800 (PST) Received: by mail-pl1-x62d.google.com with SMTP id jl24so14231535plb.8 for ; Tue, 06 Dec 2022 07:24:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=++VLLdD5R20NP2dhD9BoY4L3MuuVmiuDtlzNl1iSWtk=; b=cAilTNJHTAFkJQytHoH0SGB+6dKp6ndnZajpjXOAv2UO5kipCER/TNgAJmTUJcESYl VUtyRMqplbj+tD36ohI0lETkbFfIKMTDdyDeb35cYkms3sWCP6VCM94uPzi4In9LmbJv +2POC21Bj9oHiGiVhRrHZxnizizh3iJoxjf10= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=++VLLdD5R20NP2dhD9BoY4L3MuuVmiuDtlzNl1iSWtk=; b=mh9IwNe7Sm6XQvxLfW1nwvhyPfzf4bA5bzzNkenqDJ9Sopgf+XaPpit7fG3RN8cwFT J0gOkSDvjylNVWb0a4Iyw58DqM5ddDR9k4wIQ1B6r7mF1r7WyVWixUvGTBp27xApuvwX xMmnyMqlOK2xBMosEIz3tQhDVT9C9m3P2QCNbFHbclFkYARDJzP27hb55lIy9Frkb/Ks ynB1qnv8xeNBj6nMMw8c5wandweDOyvkmaqWJpL8ZAssAVmkgMFhcsJ5UiMcxHV9GfrM F1yzCfj11a38fsnqoYnBuH3DP46CAYCMFkpROlgqScqdRcoB4HqZMZYpoDdT+Ib52oTy y5/g== X-Gm-Message-State: ANoB5pkHyMnDfzKuEhGEKd7HnJzylM/1XMY99Y1eUV0bo4NwA5G7tYUu 6Z5xiPthJbDy4cipi8PBveld0A== X-Google-Smtp-Source: AA0mqf7aeZ4dvXiSU9Z+VNjS+yr8ocnkAalGIxhJS9tP4tTJN8fDvVoJBtGSW7msaJjFp5VgNQFYmQ== X-Received: by 2002:a17:902:ccc3:b0:189:808b:c659 with SMTP id z3-20020a170902ccc300b00189808bc659mr46888465ple.13.1670340246644; Tue, 06 Dec 2022 07:24:06 -0800 (PST) Received: from jeffxud.c.googlers.com.com (30.202.168.34.bc.googleusercontent.com. [34.168.202.30]) by smtp.gmail.com with ESMTPSA id r25-20020a635d19000000b0046b1dabf9a8sm10004686pgb.70.2022.12.06.07.24.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Dec 2022 07:24:05 -0800 (PST) From: jeffxu@chromium.org To: skhan@linuxfoundation.org, keescook@chromium.org Cc: akpm@linux-foundation.org, dmitry.torokhov@gmail.com, dverkamp@chromium.org, hughd@google.com, jeffxu@google.com, jorgelo@chromium.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, jannh@google.com, linux-hardening@vger.kernel.org, Jeff Xu Subject: [PATCH v5 4/6] mm/memfd: Add write seals when apply SEAL_EXEC to executable memfd Date: Tue, 6 Dec 2022 15:23:56 +0000 Message-Id: <20221206152358.1966099-5-jeffxu@google.com> X-Mailer: git-send-email 2.39.0.rc0.267.gcb52ba06e7-goog In-Reply-To: <20221206152358.1966099-1-jeffxu@google.com> References: <20221206152358.1966099-1-jeffxu@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Jeff Xu In order to avoid WX mappings, add F_SEAL_WRITE when apply F_SEAL_EXEC to an executable memfd, so W^X from start. This implys application need to fill the content of the memfd first, after F_SEAL_EXEC is applied, application can no longer modify the content of the memfd. Typically, application seals the memfd right after writing to it. For example: 1. memfd_create(MFD_EXEC). 2. write() code to the memfd. 3. fcntl(F_ADD_SEALS, F_SEAL_EXEC) to convert the memfd to W^X. 4. call exec() on the memfd. Signed-off-by: Jeff Xu --- mm/memfd.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/memfd.c b/mm/memfd.c index ec70675a7069..92f0a5765f7c 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -222,6 +222,12 @@ static int memfd_add_seals(struct file *file, unsigned= int seals) } } =20 + /* + * SEAL_EXEC implys SEAL_WRITE, making W^X from the start. + */ + if (seals & F_SEAL_EXEC && inode->i_mode & 0111) + seals |=3D F_SEAL_SHRINK|F_SEAL_GROW|F_SEAL_WRITE|F_SEAL_FUTURE_WRITE; + *file_seals |=3D seals; error =3D 0; =20 --=20 2.39.0.rc0.267.gcb52ba06e7-goog