From patchwork Tue Nov 20 05:25:44 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 10689867 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 70D4B13BF for ; Tue, 20 Nov 2018 05:26:15 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 60FCC29E91 for ; Tue, 20 Nov 2018 05:26:15 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4C9722A270; Tue, 20 Nov 2018 05:26:15 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=unavailable version=3.3.1 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F078229E91 for ; Tue, 20 Nov 2018 05:26:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D42D56B1C8D; Tue, 20 Nov 2018 00:26:13 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id CC9466B1CA1; Tue, 20 Nov 2018 00:26:13 -0500 (EST) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B437A6B1CA9; Tue, 20 Nov 2018 00:26:13 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from mail-pl1-f200.google.com (mail-pl1-f200.google.com [209.85.214.200]) by kanga.kvack.org (Postfix) with ESMTP id 70BA06B1C8D for ; Tue, 20 Nov 2018 00:26:13 -0500 (EST) Received: by mail-pl1-f200.google.com with SMTP id v11so605493ply.4 for ; Mon, 19 Nov 2018 21:26:13 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:from:to:cc:subject:date :message-id:mime-version:content-transfer-encoding; bh=rhPoQZhqgkEYd2R0TR94fBIobE2oIUczJVXl8rOT65A=; b=meXxEfvF9dSJaZS1Eslqz/0pqCdR/ywSSVM537PJCYK15GRUafiVI6QoY6VLRHkrcl QAYEAAbsswkSll9iBrWPhIWxH9pmcTn4Sc8qvP7oF0sJq1Apnq/BHGiwgQRhVWYHx0gh mV+mKGhIn8JoAfvLxB86m0EoCfLxHbVm/6kvjVqciuT9GGeqRl42cfGxgz3mNJyp92Up IAN1BS/EFjjCoSG3EHIrO7hI69H+L6gWpkxhYNrKCAILvPFPwL1XpUVuRZrmRVGJscjY 3LuoSBaORjM6KGpykfK1mY8jh2NkgYVGCvuEjpIC7Y7W6F3U3RtR/I+1qZS1WZvTNH1G 0TrA== X-Gm-Message-State: AGRZ1gL12iuKsmGJkIxZiU45E987Ctter9zdIT/iuFRS3VPFqqi5yO/Q ec5neyMO7eJuB4rqeTvhfMXcnJivpUjWl985k1I8IfN3auRlHLGkdWufyfI8MBx9XavXn7msXpw tgiw10iAIABBP9WCwxZB20yCbADx2lVrU9V2VDclOdvW1EJ14Mc9vaSthAbfH1fQQj9FQlh6XVW MJPaNTFv6mMfCjWewznbVdbOeRPcAvZ1CWsaDB11VcXD85JltHwTa3HFwXS9qezsHRm13hdv6+5 MKid8RTOoZpITrmuFas3Ydn59VEd3ojND83JXEQU/7MUhrlazuJ0O2gv5jo1LM/AXxNTyc/DgRv lW8A3MWaviuv7zHZ/uXe0EBlOT9sPWcVVxi6lGsfmRVC7SZgkPmWM8RIjk2Crtkn6SDZQN0qgJQ K X-Received: by 2002:a62:13c3:: with SMTP id 64mr748353pft.93.1542691573097; Mon, 19 Nov 2018 21:26:13 -0800 (PST) X-Received: by 2002:a62:13c3:: with SMTP id 64mr748332pft.93.1542691572431; Mon, 19 Nov 2018 21:26:12 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1542691572; cv=none; d=google.com; s=arc-20160816; b=0i0mmfzAihYJFBMFc6S3DP3kP8bUd/7vk1tK8mEppoMSo2Im8iDYQYmWhdKCvCGCVl aBJUIDUhjrHZh6hWRtLjbim+M4ewiVwCqqfpIj6wI8bjWeNDKdP7OMqi5YpEDw/J1roT bYwtKnm7FV4wBBnxnTTPJvMwAMkqJACWh3l1ZhPq42Ui+JAYAVccLZ80diKblvBbBu6p cxKPJGJstNGSblDcwpUptUTcr4K9M4UoE+nzxVQzluaHPBtp/XB3IdmDMSdX+/sZZ6cQ 6uo1dN9LHMG4c4jdWHYC/6TzuxlUmySfKystSI5KVYE3rcXFssKQlo5/ihgG7yF1kw7L yAyQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:dkim-signature; bh=rhPoQZhqgkEYd2R0TR94fBIobE2oIUczJVXl8rOT65A=; b=MSKGMYrb7WYBk1xx588gXfs/d/xGj9xOhh54hz6kCdoVoU/xRV/mrMf1ETdjKcc+6N AhiZKnevEDrYcY2OJmLHxwSL7NCZzgwGVcj6rmCxYwRckHwkVRQqHO3gIAYdFjvON1Ht Y6DXzvZBKd/6v8O3gKm+iMYVBHs5IlSky6u+6do/ayHEqOz3fhAOL8zK+CjmnwY7TIRg 6PuGcVH8QHBAACGt7HjjT30MCBUFmWmOAwFIDV+0DcrcHFua1DL3I9i9rSTbFX21T0tm Te3JcBh//cb2Qdt5mpXJuGae6ZcFSWhGJf+BCQeuEyyP0tG1bQ5O7tGmwKhnVOSck9gu yE5g== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@joelfernandes.org header.s=google header.b=d0VOLtUk; spf=pass (google.com: domain of joel@joelfernandes.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=joel@joelfernandes.org Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id e40sor1815885plb.21.2018.11.19.21.26.12 for (Google Transport Security); Mon, 19 Nov 2018 21:26:12 -0800 (PST) Received-SPF: pass (google.com: domain of joel@joelfernandes.org designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@joelfernandes.org header.s=google header.b=d0VOLtUk; spf=pass (google.com: domain of joel@joelfernandes.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=joel@joelfernandes.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=rhPoQZhqgkEYd2R0TR94fBIobE2oIUczJVXl8rOT65A=; b=d0VOLtUkBjUsWwJ2X8edrqI7xaMpeXVg2YL7CxPVLDyWuMqlVL4fj8yAHE+xG9IZWB 49okWuYT2X7C5NpJe5AjJQqAT6HGfIgHoCDJdB6L2zBwcDKBXsIqKRy9Z9kBBTqJQDNo Zjk7sg0hCinUvDgSYGHPVpQrBpcRqy1qz4ets= X-Google-Smtp-Source: AFSGD/VVeYLa9QA/bxhkOMA/ndTVgu3RmCtiaib129NDCRTVz6dGKpjvtQgnM2eJskFnuafM5NXj2w== X-Received: by 2002:a17:902:66e5:: with SMTP id e92-v6mr772902plk.92.1542691572002; Mon, 19 Nov 2018 21:26:12 -0800 (PST) Received: from joelaf.mtv.corp.google.com ([2620:0:1000:1601:3aef:314f:b9ea:889f]) by smtp.gmail.com with ESMTPSA id p6sm20574271pfn.53.2018.11.19.21.26.10 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 19 Nov 2018 21:26:11 -0800 (PST) From: "Joel Fernandes (Google)" To: linux-man@vger.kernel.org Cc: "Joel Fernandes (Google)" , Andrew Morton , Andy Lutomirski , Hugh Dickins , Jann Horn , John Stultz , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , Matthew Wilcox , Mike Kravetz , Shuah Khan , Stephen Rothwell Subject: [PATCH -manpage 1/2] fcntl.2: Update manpage with new memfd F_SEAL_FUTURE_WRITE seal Date: Mon, 19 Nov 2018 21:25:44 -0800 Message-Id: <20181120052545.76560-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.19.1.1215.g8438c0b245-goog MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP More details of the seal can be found in the LKML patch: https://lore.kernel.org/lkml/20181120052137.74317-1-joel@joelfernandes.org/T/#t Signed-off-by: Joel Fernandes (Google) --- man2/fcntl.2 | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/man2/fcntl.2 b/man2/fcntl.2 index 03533d65b49d..54772f94964c 100644 --- a/man2/fcntl.2 +++ b/man2/fcntl.2 @@ -1525,6 +1525,21 @@ Furthermore, if there are any asynchronous I/O operations .RB ( io_submit (2)) pending on the file, all outstanding writes will be discarded. +.TP +.BR F_SEAL_FUTURE_WRITE +If this seal is set, the contents of the file can be modified only from +existing writeable mappings that were created prior to the seal being set. +Any attempt to create a new writeable mapping on the memfd via +.BR mmap (2) +will fail with +.BR EPERM. +Also any attempts to write to the memfd via +.BR write (2) +will fail with +.BR EPERM. +This is useful in situations where existing writable mapped regions need to be +kept intact while preventing any future writes. For example, to share a +read-only memory buffer to other processes that only the sender can write to. .\" .SS File read/write hints Write lifetime hints can be used to inform the kernel about the relative