Re: [Libguestfs] [PATCH V3] virt-diff: add new virt-diff tool

On Tue, Aug 21, 2012 at 04:04:54PM +0800, Wanlong Gao wrote: [...] >>> + spid = fork (); >>> + if (spid == -1) { >>> + perror ("fork"); >>> + exit (EXIT_FAILURE); >>> + } >>> + if (spid == 0) { >>> + if (guestfs_mount_local_run (sg) == -1) >>> + exit (EXIT_FAILURE); >>> + _exit (EXIT_SUCCESS); >>> + } >>> + >>> + dpid = fork(); >>> + if (dpid == -1) { >>> + perror ("fork"); >>> + exit (EXIT_FAILURE); >>> + } >>> + if (dpid == 0) { >>> + if (guestfs_mount_local_run (dg) == -1) >>> + exit (EXIT_FAILURE); >>> + _exit (EXIT_SUCCESS); >>> + } >>> + >>> + const char *dir = argv[optind]; >>> + char system_arg[BUFSIZ]; >>> + sprintf (system_arg, "diff -urN %s%s %s%s", stempdir, dir, >>> + dtempdir, dir); >>> + sleep (5); >> >> ? > > I think I'm waiting for guest launching? No, that's the wrong thing to do. The API is in two parts: First guestfs_mount_local prepares the mount point. Second guestfs_mount_local_run causes requests to be processed. You can access the mount point after guestfs_mount_local has returned. Your process will block until guestfs_mount_local_run is called, but that doesn't matter in this case (in fact, it's what you want).

Another thing: Don't use sprintf, ever. With the wrong $TMPDIR that code above is a security hole. Since you need to quote 'dir' (since it comes from user input) you're going to have to rewrite the whole call to system(3) so that it uses fork + exec instead.

Rich.