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Tue, 03 Oct 2023 08:52:49 -0700 (PDT) MIME-Version: 1.0 References: <20230828150858.393570-1-revest@chromium.org> <20230828150858.393570-6-revest@chromium.org> <20230921183323.c990c57d0b43832b39d3e363@linux-foundation.org> In-Reply-To: <20230921183323.c990c57d0b43832b39d3e363@linux-foundation.org> From: Florent Revest Date: Tue, 3 Oct 2023 17:52:38 +0200 Message-ID: Subject: Re: [PATCH v4 5/6] mm: Add a NO_INHERIT flag to the PR_SET_MDWE prctl To: Andrew Morton 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: BDBA3C0025 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: t834m4aysuwifrasz1ghe69uc9cjeuto X-HE-Tag: 1696348370-789389 X-HE-Meta: U2FsdGVkX19e1hUVe4a8XTbw/W6mjf/JX/gfv7in9kSj4INu84KJw+UqrOtKVM7tSNr9700muNyL3/WV9vCPEHYOzodt6ElchaQCVFzLONNAq0Iqr4qG+3NPAC3TBKnuKQVC9AQohDzh+jAJ7knGNlPxyIoCB3QpMfY0D2Vac1ev8MClRuS+5gcbCBm/nxLKyLV9PTXkVjIra4eDrsobk9L/vbaIChm2GFD0o/HgXMzvzyQpwToDfXhkGGpjbBn5bfXHAEbgjutN6HT9NT/pwE+4K0slKHnoYLbylNQiTDkhd4ZDebMJEiXgSs25qPVg6D1aVNYUBSGHDmbetqn4T4D3D5/7ptCRbmIZ8OrOEBhtVabzBHk+4kPW8uuydCWceq0/ABjl3aqajgcH5MSgXry542FNzMH4o9L5RyK2aYGStXK4G3I3Tca3ZRo87iR+h4Ezph6Vz8BUyPVHotAmenoNb24CuaWv3/4EPJtHJi0YUVh86imz29udLhJ/y9pLP3xglehzZMdLoCc8ZWr8IMiT0lveOIhJiRFkN69r5F6dI/4Mg5dU/kYNiwIC6HPq1fM40+ZszOSZ0YftMKaqf3dih4jchVoDJ7eAK458yXAoM3ux5vxHHcOu5sEjQX+pdkS/Em/2C9dL6AoamXBL+1sajtRFfdFY8N9MXjmjjsFpNcfzxC0RQoo2ngEzU/WQqC3WnpyuvqHqYKP7xFH5R5kdJcTZOgKc8ubbofmd2zxGsbrrljjzMDr/Gs0KXDAltp1csY4b+KlGJuDkZYWd5HsR/kmcMrdeZEmKkijM6KlvtZaK9Ov63c8CL35Zjsmxhlk/OFAsnc3CiLotTKrLhKlsT1nVHjexH2lhNtg1cxtgFfiweILerEt0GW7L1VxPCBG3Opb5tCaDq23LsBA5RFzHntmR1NyL5y97u5/96mbgXSKkCSCu3ki5E9Qdo9uB9eKp4Yb5w4wpxLIrNKk veR/jCOc 4wqrpR76RKXxKNQ426B7e72kLuk2MX/zzZ+U0TJpcnPotNKblUZdZzoF+3IzLb2H8bn6X4nLKe3FJ7UgO8BKQX99sap0gM0YMLXsDuqBOdCVqyYLmwVpRLG003qsRhSS0+ZCHbBHc4Nn1VgR9Y8fA8A4gjACC5WbnnTCTbdz2oNSM0HX8LMzu+02gi0FryZ986exeOur4vuVnM0ZmKnPOoWI/GD5Rhq+Uc3WXtOAGFVQ7qdvpNT59Y4nafOdy82rQJxIXynekNzEtCvbWNd9fuO5wO5AlCZQWDJjfh9Tb+MSOPW91uGu+/M9aisY4QMc4oc2HSnsC/A20IH23I1hJkdN66tNlydKfaUjS2nOb9UyUQjr+T3XU428wN6zcIIGbsCnPHaZksY3KMIRxVkr8CD3+sr767eQa/IKwvJsYILGPB4nBWYvSlYofB8X1onx9SSypj8OAkqoiwRY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000063, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Sep 22, 2023 at 3:33=E2=80=AFAM Andrew Morton wrote: > > On Mon, 28 Aug 2023 17:08:57 +0200 Florent Revest w= rote: > > > 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 b= e > > 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? Ah that's a good point, I didn't think about it, thank you. > And did we update the manpage for PR_SET_MDWE? No we didn't but I sent a patch to man-pages here: https://lore.kernel.org/linux-man/20231003155010.3651349-1-revest@chromium.= org/