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[209.85.167.53]) by smtp.gmail.com with ESMTPSA id j7sm2361458lfc.16.2019.09.04.13.57.08 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Sep 2019 13:57:08 -0700 (PDT) Received: by mail-lf1-f53.google.com with SMTP id w67so135455lff.4 for ; Wed, 04 Sep 2019 13:57:08 -0700 (PDT) X-Received: by 2002:a19:f204:: with SMTP id q4mr52203lfh.29.1567630138756; Wed, 04 Sep 2019 13:48:58 -0700 (PDT) MIME-Version: 1.0 References: <20190904201933.10736-1-cyphar@cyphar.com> <20190904201933.10736-2-cyphar@cyphar.com> In-Reply-To: <20190904201933.10736-2-cyphar@cyphar.com> From: Linus Torvalds Date: Wed, 4 Sep 2019 13:48:43 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v12 01/12] lib: introduce copy_struct_{to,from}_user helpers To: Aleksa Sarai Cc: Al Viro , Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Ingo Molnar , Peter Zijlstra , Christian Brauner , Rasmus Villemoes , Eric Biederman , Andy Lutomirski , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , David Drysdale , Chanho Min , Oleg Nesterov , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Aleksa Sarai , Linux Containers , alpha , Linux API , linux-arch , Linux ARM , linux-fsdevel , linux-ia64@vger.kernel.org, Linux List Kernel Mailing , "open list:KERNEL SELFTEST FRAMEWORK" , linux-m68k , linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390 , Linux-sh list , linux-xtensa@linux-xtensa.org, sparclinux@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 4, 2019 at 1:20 PM Aleksa Sarai wrote: > > A common pattern for syscall extensions is increasing the size of a > struct passed from userspace, such that the zero-value of the new fields > result in the old kernel behaviour (allowing for a mix of userspace and > kernel vintages to operate on one another in most cases). Ack, this makes the whole series (and a few unrelated system calls) cleaner. Linus