xen: domainbuild: reopen libxenctrl interface after forking for domain watcher.

Using an existing libxenctrl handle after a fork was never
particularly safe (especially if foreign mappings existed at the time
of the fork) and the xc fd has been unavailable for many releases.

Reopen the handle after fork and therefore do away with xc_fd().

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/hw/xenpv/xen_domainbuild.c b/hw/xenpv/xen_domainbuild.c
index ac0e5ac..f9be029 100644
--- a/hw/xenpv/xen_domainbuild.c
+++ b/hw/xenpv/xen_domainbuild.c
@@ -174,12 +174,15 @@ static int xen_domain_watcher(void)
     for (i = 3; i < n; i++) {
         if (i == fd[0])
             continue;
-        if (i == xc_fd(xen_xc)) {
-            continue;
-        }
         close(i);
     }
 
+    /*
+     * Reopen xc interface, since the original is unsafe after fork
+     * and was closed above.
+     */
+    xen_xc = xc_interface_open(0, 0, 0);
+
     /* ignore term signals */
     signal(SIGINT,  SIG_IGN);
     signal(SIGTERM, SIG_IGN);