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d=linux-foundation.org; s=korg; t=1695346404; bh=hgf+/wwL2bSZ5fupqOPqm+9H6IdZ7z7D6atBwYgaMpU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=GvBwpIxI2GcAwSDRhWd3jisdO/CqiYQhel75el489tnVKctdp65xy4MD6nAy1/Vbd bQKzllRA0LKzLMLJawr/PKHxmvgomXPQ5d2DG0vqWu2ufwKQAdyAOXUNIxMHz2kvKz DcMomXaoY40mfH6QVM0j6yo5CpgZY/YG/Ud9SGtk= Date: Thu, 21 Sep 2023 18:33:23 -0700 From: Andrew Morton To: Florent Revest Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, catalin.marinas@arm.com, anshuman.khandual@arm.com, joey.gouly@arm.com, mhocko@suse.com, keescook@chromium.org, david@redhat.com, peterx@redhat.com, izbyshev@ispras.ru, broonie@kernel.org, szabolcs.nagy@arm.com, kpsingh@kernel.org, gthelen@google.com, toiwoton@gmail.com, ayush.jain3@amd.com Subject: Re: [PATCH v4 5/6] mm: Add a NO_INHERIT flag to the PR_SET_MDWE prctl Message-Id: <20230921183323.c990c57d0b43832b39d3e363@linux-foundation.org> In-Reply-To: <20230828150858.393570-6-revest@chromium.org> References: <20230828150858.393570-1-revest@chromium.org> <20230828150858.393570-6-revest@chromium.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 0C52840005 X-Stat-Signature: j4x1t3s97wr36c1ufczhxuc19a1hkurm X-Rspam-User: X-HE-Tag: 1695346409-619101 X-HE-Meta: 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 wgDNJIZc f/0G7xFiSMhvUQxIrVBKmVbrHwmlLxkGk5k/Mu02vPa4PwAIED0O0hYQa4x9pdbZn2hMantq0Ra1iI6fdicnkA5LhZYuXlMFqNQxj9UozlPQkZBjnz8456RZ20Wvlp5e5rKR2IxWO6Cadgbr5aterX2eW3GcsVTkfXtw4MFpoLv1MPyeIHglzeZEV7TOafUiz42BDtwJis1eCcEbgUakSNJNCcoOBc5z2f79N9SnZoImGpb00d3FC98WsTBlqxDJROMrn+keNaH1wCt+SlV3f/oS01x+kqpifwuhGBd55VVYP3EW66ttL9gTnFICRjz2K9GOJ0cV9CAZg9PdgZ2KymmUP3vfygjaBMmC/dD8tS27zpc8Il+JcYqOxf+C+i8ybgoi0cHA9giU84NQX/PFygiykw3ipMseVEeSl02Jovg7iJSw59YzMYI4iwA== 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: On Mon, 28 Aug 2023 17:08:57 +0200 Florent Revest wrote: > This extends the current PR_SET_MDWE prctl arg with a bit to indicate > that the process doesn't want MDWE protection to propagate to children. > > To implement this no-inherit mode, the tag in current->mm->flags must be > absent from MMF_INIT_MASK. This means that the encoding for "MDWE but > without inherit" is different in the prctl than in the mm flags. This > leads to a bit of bit-mangling in the prctl implementation. Is a manpage update planned? And did we update the manpage for PR_SET_MDWE?