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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 243EEE77198 for ; Tue, 7 Jan 2025 00:44:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 884976B00A4; Mon, 6 Jan 2025 19:44:40 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8354D6B00A6; Mon, 6 Jan 2025 19:44:40 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6FBF46B00A8; Mon, 6 Jan 2025 19:44:40 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 522DB6B00A4 for ; Mon, 6 Jan 2025 19:44:40 -0500 (EST) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id DEBB44388D for ; Tue, 7 Jan 2025 00:44:39 +0000 (UTC) X-FDA: 82978810278.19.FBC8672 Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf08.hostedemail.com (Postfix) with ESMTP id 401AA160016 for ; Tue, 7 Jan 2025 00:44:37 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Q6WHCaS2; spf=pass (imf08.hostedemail.com: domain of kees@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=kees@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1736210677; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=RCFn8fM6RzqufSiHd94o3ZyU7blalj1o29oJqR65TDw=; b=oXgt5SbX4R+QxdlvaRYdA5mwgY56Rkx3rsM9t5Z97TJSV9SYWHtM7LJi9mOb8N5X78OamT JR1EIe+wsa6BWpKgwQiWedMBdV1fYbEvnAQX19gLbXy0tCXZh+0/aCR1iWx6XknNO5ye/W JK/e4NM7J8eZs3y90U0AW0aesue0SDQ= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1736210677; a=rsa-sha256; cv=none; b=t2yrv24LqZdgD5H0cI9h+9AH712Ca2D+idwRPQrHjK/SUS1+xf3JHCe/cme2/BlDF5MRwr L6r4EykuM+iRMStlzxoazspOV0pj+E1+xY/7zxXzXLBrWM7yKNSXsWv3+CWElgpvNRMTrn CURWZ1nhVeK/sF+eAbCeYyEPID3mF8c= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Q6WHCaS2; spf=pass (imf08.hostedemail.com: domain of kees@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=kees@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 9385AA41DD3; Tue, 7 Jan 2025 00:42:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 13F6FC4CED2; Tue, 7 Jan 2025 00:44:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736210676; bh=YC/DkJPAKUsdCiz/RgqX7UN7pkyqCECAQ40nKvx3KEs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Q6WHCaS2HDXddQkTK6KnTPymgGQKyYA+Mi+z3SMY7ENDvJW1BuVxa/vxkMSSHKyTO //8e4bMU8a8bf6sxg/gXNhgJH1ksYYGTPlNArpc+jk2jm60ZbIjb2UaDWPb9yzGIwI 9yhU465GMn9gXHTLAG6/ugwyG4p0HIwVy6MnxzKgdLGgf1vsYpKQZdiGBsWprqdTf+ bw7RJuHThVn9ebZGoTLWQWrkdLBN/TAEuxSrBBF+JQVx14vySkGzOH3xlMgQzc1SMe 2/uPDYsNgF3Y3Ta86dY9Ye9WvL1FTSoPVBbdYb0Llw0subqhXETms7mxcZxr6v5IBl ZO3biR+owBatw== Date: Mon, 6 Jan 2025 16:44:33 -0800 From: Kees Cook To: Jeff Xu Cc: Jann Horn , Lorenzo Stoakes , "Isaac J. Manjarres" , Andrew Morton , Jeff Layton , Chuck Lever , Alexander Aring , "Liam R. Howlett" , Vlastimil Babka , Shuah Khan , kernel-team@android.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, Suren Baghdasaryan , Kalesh Singh , John Stultz Subject: Re: [RFC PATCH v1 1/2] mm/memfd: Add support for F_SEAL_FUTURE_EXEC to memfd Message-ID: <202501061643.986D9453@keescook> References: <20241206010930.3871336-1-isaacmanjarres@google.com> <20241206010930.3871336-2-isaacmanjarres@google.com> <0ff1c9d9-85f0-489e-a3f7-fa4cef5bb7e5@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 401AA160016 X-Stat-Signature: 9t6twx7sgzc9y7yofdik8mjdqdra76u4 X-Rspam-User: X-HE-Tag: 1736210677-260697 X-HE-Meta: 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 tow2O5YF 5pB87DxN9xfxJNFbUUPeTAteZpWDc791tKC0uV5DtaUzwf8tqVYGcSave3xBlDWP3+w8NeIs8leFnU7DvTxvi7B05gxYovpCNjEuNWGTCMmiUxdc4HNPTgMHyOjyu1f4xP+h5wG3jC5jCUqwwleXlsuUjqWRoQtNLpZcr78lK6msLyJWCEmG1afRXP8vHpVXP9sh6MhPH6SvQG21DQCQj0+WLxGM9L1qvaVUQ84Fqmpd7tWKHDoMZbDuxY/Nq1DyRXKwLOi3ilWnaZ+etHWHaWPqtOXC8uR5VyiMOqNnOKIRnhn/PoE00C3/kX7nry3bpFxSGMewYOUD6CTu2UOl6EVVskeP5cuHHoCa4LHni8xuhhpiJEljEf5LKplf/U5jQwD4g34CP8oLBFsXW+1NhiGleQY+UoqR4T50jSEB/h7SZ7QuTaixKjByRDAlE4eZcVYQy X-Bogosity: Ham, tests=bogofilter, spamicity=0.000628, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jan 06, 2025 at 10:26:27AM -0800, Jeff Xu wrote: > + Kees because this is related to W^X memfd and security. > > On Fri, Jan 3, 2025 at 7:14 AM Jann Horn wrote: > > > > On Fri, Dec 6, 2024 at 7:19 PM Lorenzo Stoakes > > wrote: > > > On Thu, Dec 05, 2024 at 05:09:22PM -0800, Isaac J. Manjarres wrote: > > > > + if (is_exec_sealed(seals)) { > > > > > > Are we intentionally disallowing a MAP_PRIVATE memfd's mapping's execution? > > > I've not tested this scenario so don't know if we somehow disallow this in > > > another way but note on write checks we only care about shared mappings. > > > > > > I mean one could argue that a MAP_PRIVATE situation is the same as copying > > > the data into an anon buffer and doing what you want with it, here you > > > could argue the same... > > > > > > So probably we should only care about VM_SHARED? > > > > FWIW I think it doesn't make sense to distinguish between > > shared/private mappings here - in the scenario described in the cover > > letter, it wouldn't matter that much to an attacker whether the > > mapping is shared or private (as long as the VMA contents haven't been > > CoWed already). > +1 on this. > The concept of blocking this for only shared mapping is questionable. Right -- why does sharedness matter? It seems more robust to me to not create a corner case but rather apply the flag/behavior universally? -- Kees Cook