Re: [libvirt] PATCH: 4/5: Support daemonizing child & env variables

Some of the existing usage of fork/exec in libvirt is done such that the child process is daemonized. In particular the libvirt_proxy and the auto-spawned libvirtd for qemu:///session. Since we want to switch these to use virExec, we need to suport a daemon mode. This patch removes the two alternate virExec and virExecNonBlock functions and renames the internal __virExec to virExec. It then gains a 'flags' parameter which can be used to specify non-blocking mode, or daemon mode. We also add the ability to pass in a list of environment variables which get passed on to execve(). We also now explicitly close all file handles. Although libvirt code is careful to set O_CLOSEXEC on all its file handles, in multi-threaded apps there is a race condition between opening a FD and setting O_CLOSEXEC. Furthermore, we can't guarentee that all applications using libvirt are careful to set O_CLOSEXEC. Leaking FDs to a child is a potential security risk and often causes SELinux AVCs to be raised. Thus explicitely closing all FDs is a important safety net.

diff -r 28ddf9f5791c src/util.c

+ for (i = 3; i < openmax; i++) + if (i != infd && + i != null && + i != childout && + i != childerr) + close(i); + + if (flags & VIR_EXEC_DAEMON) { + if (setsid() < 0) { + ReportError(conn, VIR_ERR_INTERNAL_ERROR, + _("cannot become session leader: %s"), + strerror(errno)); + _exit(1); + } + + if (chdir("/") < 0) { + ReportError(conn, VIR_ERR_INTERNAL_ERROR, + _("cannot change to root directory: %s"), + strerror(errno)); + _exit(1); + } + + pid = fork();