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Mon, 21 Jun 2021 13:07:10 +0200 (CEST) Date: Mon, 21 Jun 2021 13:07:10 +0200 From: Gerd Hoffmann To: Markus Armbruster Subject: Re: [PATCH v2] ui/gtk: Allow user to select monitor number to display qemu in full screen through new gtk display option Message-ID: <20210621110710.u7stl5la2cp5mlqw@sirius.home.kraxel.org> References: <20210617020609.18089-1-swee.aun.khor@intel.com> <8735tfsa79.fsf@dusky.pond.sub.org> <20210621065148.o7yggutrxgvdnpc7@sirius.home.kraxel.org> <875yy739hv.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <875yy739hv.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kraxel@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=kraxel@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.373, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Khor, Swee Aun" , "Romli, Khairul Anuar" , "eblake@redhat.com" , "Kasireddy, Vivek" , "qemu-devel@nongnu.org" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" > > I don't think qemu has to worry much here, and trying to automatically > > adapt to hot-plugged monitors might even have bad interactions with > > whatever the display server is going to do. > > I'm concerned there is a TOCTTOU issue: > > if (opts->u.gtk.has_monitor) { > int n_monitor; > 1. n_monitor = gdk_display_get_n_monitors(window_display); > > 2. if ((opts->u.gtk.monitor <= n_monitor) && > (opts->u.gtk.monitor > 0)) { > GdkScreen *gdk_screen; > gdk_screen = gdk_display_get_default_screen(window_display); > 3. gtk_window_fullscreen_on_monitor(GTK_WINDOW(s->window), gdk_screen, > (opts->u.gtk.monitor - 1)); > } else { > fprintf(stderr, "Invalid GTK monitor argument\n"); > } > } > > If monitors can go at any time, then the check 2. cannot ensure we pass > a valid monitor number at 3. > > I asked what happens when we pass an invalid monitor number. I'm not > sure I understand sweeaun's answer. > > If what happens is sane, then why have check 2.? gtk_window_fullscreen_on_monitor() seems to be a "best effort" offer and it doesn't return error codes. So catching possible user errors looks useful to me. The code should use error_report instead though (or maybe warn_report given this is not fatal). Reporting the valid range is probably a good idea too. take care, Gerd