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 AF878C87FC5 for ; Thu, 24 Jul 2025 22:29:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5214E8E00BF; Thu, 24 Jul 2025 18:29:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4F8D78E007C; Thu, 24 Jul 2025 18:29:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 435B88E00BF; Thu, 24 Jul 2025 18:29:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 34D7F8E007C for ; Thu, 24 Jul 2025 18:29:39 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 65FB3133B75 for ; Thu, 24 Jul 2025 22:29:38 +0000 (UTC) X-FDA: 83700601236.22.6DAF6AA Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf16.hostedemail.com (Postfix) with ESMTP id 00F00180009 for ; Thu, 24 Jul 2025 22:29:36 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=MqbfNbPD; spf=pass (imf16.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-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1753396177; a=rsa-sha256; cv=none; b=G2NuAyW36pxeHPG+NMaJYtlwjOM0Kn1UOK8W3kmM9Cnlz7VhdKh5xulnkmgPWf0rp+//bw 3swXj7a3YhcnJHVjs8Ahnl0NI65R/O15n/386WS0bZkbhI39j1S1EYnwckvGOgP5Ev60EJ 50UmfOGu4y3H8N9kFQ0KU9eyjWaCbJA= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=MqbfNbPD; spf=pass (imf16.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=1753396177; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=iYOjOEXV/d4hZiplRdaSSTLgcOrC+WpUd8xUFU9tOAE=; b=vCyKLVNeHMjqIlEaqYGQLtikw02LnOPtVaQMRSbpScL7/Vc8Kc/27l2UPCSsNaJOVMRRuA 7INzluWn3vMo+YwuSzOLolMYpWdlPHgKNM9ohol0c/4hahjCZjcqf8Ci67+Zzps5naSYCL GRAcF+yhpZWfQnM+YuKhRXeFrZ1lt2c= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 4B913A5628C; Thu, 24 Jul 2025 22:29:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ECD4FC4CEED; Thu, 24 Jul 2025 22:29:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753396176; bh=W+PLhvsmzTgMSVd5jUXqYnhed16MMxVnE25H0ac9/Pg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MqbfNbPDaviGnvO64ciSpBqc/ox0Jl7XneeIO8AVezVenHude+I/K2YyWwGr39t9N Bc5nu38G37xNaZnUluI0HsBJqyGkKbaK9TUxmVu2DMJmYlyIW9VCQ8u3XsqOqB3TSG rbcnnHQVI8ALO80+JF/kmon5qcGn6Clkpt7RYWqU5WPwKNr6rFibbeluZIqnkNC1Ud 8Sr+R3Bwy59Tfn/FVFetQPWlI+xFAWsxew6nKq8yJPU6F+OGd+debCHPN/clEP+YxX Bu4hL+mxNV4t05wexN2LVwyT7xs0iPsKVLYrW0VA5cxR/Ndc5kh6AN0BU9MiwWHivO clndEu5FCvSrg== Date: Thu, 24 Jul 2025 15:29:35 -0700 From: Kees Cook To: David Hildenbrand Cc: Lorenzo Stoakes , Andrew Morton , "Liam R . Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jeff Xu Subject: Re: [PATCH v3 2/5] mm/mseal: update madvise() logic Message-ID: <202507241528.A73E1178@keescook> References: <202507241352.22634450C9@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 00F00180009 X-Stat-Signature: knd41csdjqet3sbus3o6itp8qefahg5t X-HE-Tag: 1753396176-640944 X-HE-Meta: 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 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: List-Subscribe: List-Unsubscribe: On Thu, Jul 24, 2025 at 11:41:04PM +0200, David Hildenbrand wrote: > On 24.07.25 23:32, David Hildenbrand wrote: > > > As an aside, why should discard work in this case even without step 4? > > > Wouldn't setting "read-only" imply you don't want the memory to change > > > out from under you? I guess I'm not clear on the semantics: how do memory > > > protection bits map to madvise actions like this? > > > > They generally don't affect MADV_DONTNEED behavior. The only documented > > (man page) reason for EPERM in the man page is related to MADV_HWPOISON. > > > > (Exception: MADV_POPULATE_READ/MADV_POPULATE_WRITE requires corresponding > permissions) Shouldn't an MADV action that changes memory contents require the W bit though? I mean, I assume the ship may have sailed on this, but it feels mismatched to me. -- Kees Cook