qemu: Label all TAP FDs

https://bugzilla.redhat.com/show_bug.cgi?id=1095636

When starting up the domain the domain's NICs are allocated. As of
1f24f682 (v1.0.6) we are able to use multiqueue feature on virtio
NICs. It breaks network processing into multiple queues which can be
processed in parallel by different host CPUs. The queues are, however,
created by opening /dev/net/tun several times. Unfortunately, only the
first FD in the row is labelled so when turning the multiqueue feature
on in the guest, qemu will get AVC denial. Make sure we label all the
FDs needed.

Moreover, the default label of /dev/net/tun doesn't allow
attaching a queue:

    type=AVC msg=audit(1399622478.790:893): avc:  denied  { attach_queue }
    for  pid=7585 comm="qemu-kvm"
    scontext=system_u:system_r:svirt_t:s0:c638,c877
    tcontext=system_u:system_r:virtd_t:s0-s0:c0.c1023
    tclass=tun_socket

And as suggested by SELinux maintainers, the tun FD should be labeled
as svirt_t. Therefore, we don't need to adjust any range (as done
previously by Guannan in ae368ebf) rather set the seclabel of the
domain directly.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_command.c

@@ -192,10 +192,6 @@ qemuPhysIfaceConnect(virDomainDefPtr def,
         vmop, cfg->stateDir,
         virDomainNetGetActualBandwidth(net));
     if (rc >= 0) {
-        if (virSecurityManagerSetTapFDLabel(driver->securityManager,
-                                            def, rc) < 0)
-            goto error;
-
         virDomainAuditNetDevice(def, net, res_ifname, true);
         VIR_FREE(net->ifname);
         net->ifname = res_ifname;
@@ -203,17 +199,6 @@ qemuPhysIfaceConnect(virDomainDefPtr def,
 
     virObjectUnref(cfg);
     return rc;
-
- error:
-    ignore_value(virNetDevMacVLanDeleteWithVPortProfile(
-                     res_ifname, &net->mac,
-                     virDomainNetGetActualDirectDev(net),
-                     virDomainNetGetActualDirectMode(net),
-                     virDomainNetGetActualVirtPortProfile(net),
-                     cfg->stateDir));
-    VIR_FREE(res_ifname);
-    virObjectUnref(cfg);
-    return -1;
 }
 
 
@@ -7201,6 +7186,9 @@ qemuBuildInterfaceCommandLine(virCommandPtr cmd,
     }
 
     for (i = 0; i < tapfdSize; i++) {
+        if (virSecurityManagerSetTapFDLabel(driver->securityManager,
+                                            def, tapfd[i]) < 0)
+            goto cleanup;
         virCommandPassFD(cmd, tapfd[i],
                          VIR_COMMAND_PASS_FD_CLOSE_PARENT);
         if (virAsprintf(&tapfdName[i], "%d", tapfd[i]) < 0)

src/qemu/qemu_hotplug.c

@@ -948,6 +948,12 @@ int qemuDomainAttachNetDevice(virConnectPtr conn,
             goto cleanup;
     }
 
+    for (i = 0; i < tapfdSize; i++) {
+        if (virSecurityManagerSetTapFDLabel(driver->securityManager,
+                                            vm->def, tapfd[i]) < 0)
+            goto cleanup;
+    }
+
     if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_NET_NAME) ||
         virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE)) {
         if (qemuAssignDeviceNetAlias(vm->def, net, -1) < 0)

src/security/security_selinux.c

@@ -2330,47 +2330,17 @@ virSecuritySELinuxSetImageFDLabel(virSecurityManagerPtr mgr ATTRIBUTE_UNUSED,
 }
 
 static int
-virSecuritySELinuxSetTapFDLabel(virSecurityManagerPtr mgr,
+virSecuritySELinuxSetTapFDLabel(virSecurityManagerPtr mgr ATTRIBUTE_UNUSED,
                                 virDomainDefPtr def,
                                 int fd)
 {
-    struct stat buf;
-    security_context_t fcon = NULL;
     virSecurityLabelDefPtr secdef;
-    char *str = NULL;
-    int rc = -1;
 
     secdef = virDomainDefGetSecurityLabelDef(def, SECURITY_SELINUX_NAME);
     if (!secdef || !secdef->label)
         return 0;
 
-    if (fstat(fd, &buf) < 0) {
-        virReportSystemError(errno, _("cannot stat tap fd %d"), fd);
-        goto cleanup;
-    }
-
-    if ((buf.st_mode & S_IFMT) != S_IFCHR) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("tap fd %d is not character device"), fd);
-        goto cleanup;
-    }
-
-    if (getContext(mgr, "/dev/tap.*", buf.st_mode, &fcon) < 0) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("cannot lookup default selinux label for tap fd %d"), fd);
-        goto cleanup;
-    }
-
-    if (!(str = virSecuritySELinuxContextAddRange(secdef->label, fcon))) {
-        goto cleanup;
-    } else {
-        rc = virSecuritySELinuxFSetFilecon(fd, str);
-    }
-
- cleanup:
-    freecon(fcon);
-    VIR_FREE(str);
-    return rc;
+    return virSecuritySELinuxFSetFilecon(fd, secdef->label);
 }
 
 static char *