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[209.85.208.172]) by smtp.gmail.com with ESMTPSA id n17sm3852011ljc.76.2020.04.02.12.27.09 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 02 Apr 2020 12:27:09 -0700 (PDT) Received: by mail-lj1-f172.google.com with SMTP id k21so4546945ljh.2 for ; Thu, 02 Apr 2020 12:27:09 -0700 (PDT) X-Received: by 2002:a2e:8911:: with SMTP id d17mr2938169lji.16.1585855628859; Thu, 02 Apr 2020 12:27:08 -0700 (PDT) MIME-Version: 1.0 References: <27106d62fdbd4ffb47796236050e418131cb837f.1585811416.git.christophe.leroy@c-s.fr> <20200402162942.GG23230@ZenIV.linux.org.uk> <67e21b65-0e2d-7ca5-7518-cec1b7abc46c@c-s.fr> <20200402175032.GH23230@ZenIV.linux.org.uk> <202004021132.813F8E88@keescook> In-Reply-To: <202004021132.813F8E88@keescook> From: Linus Torvalds Date: Thu, 2 Apr 2020 12:26:52 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH RESEND 1/4] uaccess: Add user_read_access_begin/end and user_write_access_begin/end To: Kees Cook Cc: Al Viro , Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Dave Airlie , Daniel Vetter , Andrew Morton , Peter Anvin , Linux Kernel Mailing List , linuxppc-dev , Linux-MM , linux-arch , Russell King , Christian Borntraeger Content-Type: text/plain; charset="UTF-8" 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 Thu, Apr 2, 2020 at 11:36 AM Kees Cook wrote: > > Yup, I think it's a weakness of the ARM implementation and I'd like to > not extend it further. AFAIK we should never nest, but I would not be > surprised at all if we did. Wel, at least the user_access_begin/end() sections can't nest. objtool verifies and warns about that on x86. > If we were looking at a design goal for all architectures, I'd like > to be doing what the public PaX patchset We already do better than PaX ever did. Seriously. Mainline has long since passed their hacky garbage. Plus PaX and grsecurity should be actively shunned. Don't look at it, don't use it, and tell everybody you know to not use that shit. Linus