[PATCH] utils/settrans: fix the teardown of chrooted environments

[Justus Winter]

Previously, settrans --chroot would just exec the target.  Create a
new process for that purpose.  Wait for its completion, then ask the
translator (nicely by default) to go away.  If it refuses with EBUSY,
it might be because some process has daemonized inside the chrooted
environment.

This fixes the following bug when settrans is used with fakeroot:

% fakeroot-hurd /bin/true 2>&1 | tee
<hangs>

Here, fakeroot-hurd execs settrans with --chroot, settrans execs
/hurd/fakeauth which will eventually exec the target /bin/true.  When
true terminates, it will close its stdout and stderr.  But
/hurd/fakeroot's stderr is also connected to tee's stdin, preventing
tee from exiting.

* utils/settrans.c (main): Fix the teardown of chrooted environments.
---
 utils/settrans.c |   69 ++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 44 insertions(+), 25 deletions(-)

diff --git a/utils/settrans.c b/utils/settrans.c
index d13e7c4..ecc6d75 100644
--- a/utils/settrans.c
+++ b/utils/settrans.c
@@ -25,6 +25,7 @@
 #include <error.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <sys/wait.h>
 
 #include <error.h>
 #include <argz.h>
@@ -279,33 +280,51 @@ main(int argc, char *argv[])
 
   if (chroot_command)
     {
-      /* We will act as the parent filesystem would for a lookup
-        of the active translator's root node, then use this port
-        as our root directory while we exec the command.  */
-
-      char retry_name[1024];   /* XXX */
-      retry_type do_retry;
-      mach_port_t root;
-      err = fsys_getroot (active_control,
-                         MACH_PORT_NULL, MACH_MSG_TYPE_COPY_SEND,
-                         NULL, 0, NULL, 0, 0, &do_retry, retry_name, &root);
-      mach_port_deallocate (mach_task_self (), active_control);
-      if (err)
-       error (6, err, "fsys_getroot");
-      err = hurd_file_name_lookup_retry (&_hurd_ports_use, &getdport, 0,
-                                        do_retry, retry_name, 0, 0,
-                                        &root);
-      if (err)
-       error (6, err, "cannot resolve root port");
+      pid_t pid;
+      switch ((pid = fork ()))
+       {
+       case -1:
+         error (6, errno, "fork");
+
+       case 0:; /* Child.  */
+         /* We will act as the parent filesystem would for a lookup
+            of the active translator's root node, then use this port
+            as our root directory while we exec the command.  */
+
+         char retry_name[1024];        /* XXX */
+         retry_type do_retry;
+         mach_port_t root;
+         err = fsys_getroot (active_control,
+                             MACH_PORT_NULL, MACH_MSG_TYPE_COPY_SEND,
+                             NULL, 0, NULL, 0, 0,
+                             &do_retry, retry_name, &root);
+         mach_port_deallocate (mach_task_self (), active_control);
+         if (err)
+           error (6, err, "fsys_getroot");
+         err = hurd_file_name_lookup_retry (&_hurd_ports_use, &getdport, 0,
+                                            do_retry, retry_name, 0, 0,
+                                            &root);
+         if (err)
+           error (6, err, "cannot resolve root port");
+
+         if (setcrdir (root))
+           error (7, errno, "cannot install root port");
+         mach_port_deallocate (mach_task_self (), root);
+         if (chdir ("/"))
+           error (8, errno, "cannot chdir to new root");
+
+         execvp (chroot_command[0], chroot_command);
+         error (8, errno, "cannot execute %s", chroot_command[0]);
+         break;
 
-      if (setcrdir (root))
-       error (7, errno, "cannot install root port");
-      mach_port_deallocate (mach_task_self (), root);
-      if (chdir ("/"))
-       error (8, errno, "cannot chdir to new root");
+       default: /* Parent.  */
+         if (waitpid (pid, NULL, 0) == -1)
+           error (8, errno, "waitpid");
 
-      execvp (chroot_command[0], chroot_command);
-      error (8, errno, "cannot execute %s", chroot_command[0]);
+         err = fsys_goaway (active_control, goaway_flags);
+         if (err && err != EBUSY)
+           error (9, err, "fsys_goaway");
+       }
     }
 
   return 0;
-- 
1.7.10.4