launch: Avoid double-close when qemu exits early.

The stdin and stdout of the qemu process are aliased to g->fd:

  g->fd[0] = wfd[1];
  g->fd[1] = rfd[0];

However if the child exits early, then child_cleanup closes g->fd[0],
g->fd[1], AND the code at the cleanup1 label closes wfd[1], rfd[0],
resulting in a double-close.

Avoid this case by setting wfd[1], rfd[0] to -1.  In the cleanup1
label, only close wfd[1], rfd[0] if they are not -1, and add the same
for g->fd[0], g->fd[1].

1 files changed, 6 insertions, 2 deletions

diff --git a/src/launch.c b/src/launch.c
index 86e1bc56..3cd16f41 100644
--- a/src/launch.c
+++ b/src/launch.c
@@ -1018,6 +1018,7 @@ launch_appliance (guestfs_h *g)
 
     g->fd[0] = wfd[1];		/* stdin of child */
     g->fd[1] = rfd[0];		/* stdout of child */
+    wfd[1] = rfd[0] = -1;
   } else {
     g->fd[0] = open ("/dev/null", O_RDWR|O_CLOEXEC);
     if (g->fd[0] == -1) {
@@ -1028,6 +1029,7 @@ launch_appliance (guestfs_h *g)
     if (g->fd[1] == -1) {
       perrorf (g, "dup");
       close (g->fd[0]);
+      g->fd[0] = -1;
       goto cleanup1;
     }
   }
@@ -1098,13 +1100,15 @@ launch_appliance (guestfs_h *g)
 
  cleanup1:
   if (!g->direct) {
-    close (wfd[1]);
-    close (rfd[0]);
+    if (wfd[1] >= 0) close (wfd[1]);
+    if (rfd[1] >= 0) close (rfd[0]);
   }
   if (g->pid > 0) kill (g->pid, 9);
   if (g->recoverypid > 0) kill (g->recoverypid, 9);
   if (g->pid > 0) waitpid (g->pid, NULL, 0);
   if (g->recoverypid > 0) waitpid (g->recoverypid, NULL, 0);
+  if (g->fd[0] >= 0) close (g->fd[0]);
+  if (g->fd[1] >= 0) close (g->fd[1]);
   g->fd[0] = -1;
   g->fd[1] = -1;
   g->pid = 0;