Le dim. 28 juil. 2013 10:12:37 CEST, Richard Weinberger a écrit : > Am 27.07.2013 17:23, schrieb Gabriel de Perthuis: >> Useful for >> * limiting privileges >> * opening block devices O_EXCL > > So, the goal of this patch is to allow passing a file descriptor > number as block device instead of a file?
Yes. It turns out it already works, but not after dropping privileges. > I assume you have already a wrapper around UML which exec()'s it such that > it can reuse a fd? Yes, vido: https://github.com/g2p/vido Here's the relevant commit: https://github.com/g2p/vido/commit/42d4b86eab13d90ee63138b73146485dc4e47ec6 >> Use dup to work around the fact /proc/self/fd >> can't be opened after dropping privileges. >> This proc behaviour doesn't match TLPI and might be a bug. >> >> Qemu has a slightly more complex fdset approach >> that provides fds with different access permissions. > > I really don't like that you patch os_open_file(), this is a > generic function. The justification was that it unbreaks open("/dev/fd") to be more like standards suggest, but I can see how that makes it a special case. > What about this one? > Allow ubda= (and all other UML block device kernel parameters) to > accept arguments like file:/foo/bar and fd:N. > Where N is a number and file: is default such that we do not break > old kernels. Okay, I'll add a prefix. Maybe file:// + /abs/path | rel/path since that's already standard. ------------------------------------------------------------------------------ See everything from the browser to the database with AppDynamics Get end-to-end visibility with application monitoring from AppDynamics Isolate bottlenecks and diagnose root cause in seconds. Start your free trial of AppDynamics Pro today! http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
