On 2018-02-02 11:11 PM, Keith Packard wrote: > Michel Dänzer <mic...@daenzer.net> writes: > >> But this seems irrelevant for per-window flips. In this case, the window >> pixmap isn't used for anything else after flipping, so having direct >> access to the pixmap doesn't allow the client to do anything it couldn't >> do anyway using the X11 protocol. (There might be exceptions to this if >> the window wasn't created by the presenting client, and the Security >> extension comes into play. But that would be a rather exotic scenario, >> so I don't think we need to consider it here.) > > Agreed. Discarding the window pixmap during per-window flips seems like > it should be fine. Of course, you need to replace the window pixmap for > all windows sharing the original redirection, and that might include the > parent. That's mildly concerning as now the client has control over the > contents of another application's window outside of the X protocol.
Ignoring the Security extension, the client has the same control over the contents of another application's window *using* the X protocol, doesn't it? If this is a concern, Present could try allocating a new window pixmap to unflip to, and just leave the last flip pixmap as the window pixmap if that fails (which it "never" will, in basically any scenario where the X server can otherwise continue working normally). -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer _______________________________________________ xorg-devel@lists.x.org: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: https://lists.x.org/mailman/listinfo/xorg-devel
