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Levin" , Gleb Fotengauer-Malinovskiy , Hugh Dickins , Jan Kara , Jonathan Corbet , Mel Gorman , Mike Kravetz , Mike Rapoport , Nadav Amit , Peter Xu , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , zhangyi , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v3 2/6] userfaultfd: add /dev/userfaultfd for fine grained access control Message-Id: <20220613145540.1c9f7750092911bae1332b92@linux-foundation.org> In-Reply-To: <20220601210951.3916598-3-axelrasmussen@google.com> References: <20220601210951.3916598-1-axelrasmussen@google.com> <20220601210951.3916598-3-axelrasmussen@google.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-8.3 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 1 Jun 2022 14:09:47 -0700 Axel Rasmussen wrote: > To achieve this, add a /dev/userfaultfd misc device. This device > provides an alternative to the userfaultfd(2) syscall for the creation > of new userfaultfds. The idea is, any userfaultfds created this way will > be able to handle kernel faults, without the caller having any special > capabilities. Access to this mechanism is instead restricted using e.g. > standard filesystem permissions. The use of a /dev node isn't pretty. Why can't this be done by tweaking sys_userfaultfd() or by adding a sys_userfaultfd2()? Peter, will you be completing review of this patchset?