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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-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, Mike Rapoport Subject: Re: [PATCH v6 2/5] userfaultfd: add /dev/userfaultfd for fine grained access control Message-ID: References: <20220817214728.489904-1-axelrasmussen@google.com> <20220817214728.489904-3-axelrasmussen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-7.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED 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 Thu, Aug 18, 2022 at 08:26:38AM +0200, Greg KH wrote: > On Wed, Aug 17, 2022 at 02:47:25PM -0700, Axel Rasmussen wrote: > > +static int userfaultfd_dev_open(struct inode *inode, struct file *file) > > +{ > > + return 0; > > If your open does nothing, no need to list it here at all, right? > > > +} > > + > > +static long userfaultfd_dev_ioctl(struct file *file, unsigned int cmd, unsigned long flags) > > +{ > > + if (cmd != USERFAULTFD_IOC_NEW) > > + return -EINVAL; > > + > > + return new_userfaultfd(flags); > > +} > > + > > +static const struct file_operations userfaultfd_dev_fops = { > > + .open = userfaultfd_dev_open, > > + .unlocked_ioctl = userfaultfd_dev_ioctl, > > + .compat_ioctl = userfaultfd_dev_ioctl, > > Why do you need to set compat_ioctl? Shouldn't it just default to the > existing one? > > And why is this a device node at all? Shouldn't the syscall handle all > of this (to be honest, I didn't read anything but the misc code, sorry.) Ah, read the documentation now. Seems you want to make it easier for people to get permissions on a system. Doesn't seem wise, but hey, it's not my feature... thanks, greg k-h