From a7cc039dc796f541793955598377807af48341fb Mon Sep 17 00:00:00 2001
From: Michal Privoznik <mprivozn@redhat.com>
Date: May 03 2017 15:23:03 +0000
Subject: qemuDomainBuildNamespace: Move /dev/* mountpoints later


When setting up mount namespace for a qemu domain the following
steps are executed:

1) get list of mountpoints under /dev/
2) move them to /var/run/libvirt/qemu/$domName.ext
3) start constructing new device tree under /var/run/libvirt/qemu/$domName.dev
4) move the mountpoint of the new device tree to /dev
5) restore original mountpoints from step 2)

Note the problem with this approach is that if some device in step
3) requires access to a mountpoint from step 2) it will fail as
the mountpoint is not there anymore. For instance consider the
following domain disk configuration:

    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/dev/shm/vhostmd0'/>
      <target dev='vdb' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>
    </disk>

In this case operation fails as we are unable to create vhostmd0
in the new device tree because after step 2) there is no /dev/shm
anymore. Leave aside fact that we shouldn't try to create devices
living in other mountpoints. That's a separate bug that will be
addressed later.

Currently, the order described above is rearranged to:

1) get list of mountpoints under /dev/
2) start constructing new device tree under /var/run/libvirt/qemu/$domName.dev
3) move them to /var/run/libvirt/qemu/$domName.ext
4) move the mountpoint of the new device tree to /dev
5) restore original mountpoints from step 3)

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Cedric Bosdonnat <cbosdonnat@suse.com>

---

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 13fd706..9e51fc0 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -8029,6 +8029,30 @@ qemuDomainBuildNamespace(virQEMUDriverConfigPtr cfg,
     if (qemuDomainSetupDev(cfg, mgr, vm, devPath) < 0)
         goto cleanup;
 
+    if (qemuDomainSetupAllDisks(cfg, vm, devPath) < 0)
+        goto cleanup;
+
+    if (qemuDomainSetupAllHostdevs(cfg, vm, devPath) < 0)
+        goto cleanup;
+
+    if (qemuDomainSetupAllMemories(cfg, vm, devPath) < 0)
+        goto cleanup;
+
+    if (qemuDomainSetupAllChardevs(cfg, vm, devPath) < 0)
+        goto cleanup;
+
+    if (qemuDomainSetupTPM(cfg, vm, devPath) < 0)
+        goto cleanup;
+
+    if (qemuDomainSetupAllGraphics(cfg, vm, devPath) < 0)
+        goto cleanup;
+
+    if (qemuDomainSetupAllInputs(cfg, vm, devPath) < 0)
+        goto cleanup;
+
+    if (qemuDomainSetupAllRNGs(cfg, vm, devPath) < 0)
+        goto cleanup;
+
     /* Save some mount points because we want to share them with the host */
     for (i = 0; i < ndevMountsPath; i++) {
         struct stat sb;
@@ -8056,30 +8080,6 @@ qemuDomainBuildNamespace(virQEMUDriverConfigPtr cfg,
             goto cleanup;
     }
 
-    if (qemuDomainSetupAllDisks(cfg, vm, devPath) < 0)
-        goto cleanup;
-
-    if (qemuDomainSetupAllHostdevs(cfg, vm, devPath) < 0)
-        goto cleanup;
-
-    if (qemuDomainSetupAllMemories(cfg, vm, devPath) < 0)
-        goto cleanup;
-
-    if (qemuDomainSetupAllChardevs(cfg, vm, devPath) < 0)
-        goto cleanup;
-
-    if (qemuDomainSetupTPM(cfg, vm, devPath) < 0)
-        goto cleanup;
-
-    if (qemuDomainSetupAllGraphics(cfg, vm, devPath) < 0)
-        goto cleanup;
-
-    if (qemuDomainSetupAllInputs(cfg, vm, devPath) < 0)
-        goto cleanup;
-
-    if (qemuDomainSetupAllRNGs(cfg, vm, devPath) < 0)
-        goto cleanup;
-
     if (virFileMoveMount(devPath, "/dev") < 0)
         goto cleanup;