From patchwork Fri Dec 9 16:04:51 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Xu X-Patchwork-Id: 632744 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 27B72C4708D for ; Fri, 9 Dec 2022 16:05:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230248AbiLIQFa (ORCPT ); Fri, 9 Dec 2022 11:05:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50286 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229785AbiLIQFW (ORCPT ); Fri, 9 Dec 2022 11:05:22 -0500 Received: from mail-pf1-x42e.google.com (mail-pf1-x42e.google.com [IPv6:2607:f8b0:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 610C151306 for ; Fri, 9 Dec 2022 08:05:04 -0800 (PST) Received: by mail-pf1-x42e.google.com with SMTP id c7so3983239pfc.12 for ; Fri, 09 Dec 2022 08:05:04 -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=FZNFa0Som2cEXdyImA0PHzAPIxujgLNI2oeSKx5nHZI=; b=h3FquO7MkL3Xkcl57UR0vuuniHUg5+pjAS+449C9zKHXjh3bfCzGniHHohZYn5ZJxa PimfhG0DETXRYTKLCZGzQghCrFbpOJpZG5Zr0M0bfkbC/VGkO9Ut1cdT7lGwEdufbrrc PnxV8fbesmJTL6d00qwrsh707SkFtLJvebIYI= 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=FZNFa0Som2cEXdyImA0PHzAPIxujgLNI2oeSKx5nHZI=; b=SxVivI4jv95qPqKCKMXwqZIZkFBRIEoGySK6w+jMoSaA6HKxpl2ZeDiDqmPPe0Wshm murtiutosZkfjl7JqPANfkYplbjGp1rujLn5sCLRiTsvJNeyYYtb8x+Celhn3Wkif6jG lfqKcJVJFBsv8cpH8/VGkA9YzaxN8tvAApyGzlehH9AeUWBfCczrHKFI6OHHyJRekCsf JMFox691NHHSf7WlAL3ce7JCviwQnsW80ZgLodMmyqrNmJkF8Hpl7HVV0GjQQZ0n6s+J hdigREnCG7NuIu/h/YU5hWbqHK9ZiByWUwLI/UEuuhKAnO3W4AFqlYElpkGN97wmV9We Zhdg== X-Gm-Message-State: ANoB5pl7eWq3GplZ4op+dxQCGkajS4KF+Sv/fAbcX/PFU8S42b5VUiko wwSoyJuF9ycVJYaXLYYZ1Zu34w== X-Google-Smtp-Source: AA0mqf6CmbxiVSZwu0zBPseh9ltyuMQpEJZ+0MzUajuKI0ToOlPtqG4/ib2Rp5GkK3d0hKasOROV5Q== X-Received: by 2002:a05:6a00:a05:b0:566:900d:6396 with SMTP id p5-20020a056a000a0500b00566900d6396mr8624787pfh.22.1670601903758; Fri, 09 Dec 2022 08:05:03 -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 a15-20020aa795af000000b00576670cc170sm1460504pfk.93.2022.12.09.08.05.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Dec 2022 08:05:03 -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, linux-security-module@vger.kernel.org Subject: [PATCH v7 4/6] mm/memfd: Add write seals when apply SEAL_EXEC to executable memfd Date: Fri, 9 Dec 2022 16:04:51 +0000 Message-Id: <20221209160453.3246150-5-jeffxu@google.com> X-Mailer: git-send-email 2.39.0.rc1.256.g54fd8350bd-goog In-Reply-To: <20221209160453.3246150-1-jeffxu@google.com> References: <20221209160453.3246150-1-jeffxu@google.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org 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 Reviewed-by: Kees Cook --- 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) } } + /* + * SEAL_EXEC implys SEAL_WRITE, making W^X from the start. + */ + if (seals & F_SEAL_EXEC && inode->i_mode & 0111) + seals |= F_SEAL_SHRINK|F_SEAL_GROW|F_SEAL_WRITE|F_SEAL_FUTURE_WRITE; + *file_seals |= seals; error = 0;