[libvirt] [PATCH] nwfilter: Partly initialize driver even for non-privileged users

[Michal Privoznik]

https://bugzilla.redhat.com/show_bug.cgi?id=1211436

This reverts commit b7829f959b33c6e32422222a9ed745c0da7dc696.

The previous fix was not correct. Like everywhere else, a driver is a
global variable allocated in stateInitialize function (or something
similar for stateless drivers). Later, when a driver API is called,
it's possible that the global variable is accessed and dereferenced.
Now, some drivers require root privileges because they undertake some
actions reserved only for the system admin (e.g. manipulating host
firewall). And here's the trouble, the NWFilter state initializer
exited too early when finding out it's running unprivileged, leaving
the global NWFilter driver variable uninitialized. Any subsequent
API call that tried to lock the driver resulted in dereferencing the
driver and thus crash.

On the other hand, in order to not resurrect the bug the original
commit was fixing, Let's forbid the nwfilter define in session mode.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>

Conflicts:
	src/nwfilter/nwfilter_driver.c: Context. Code changed a bit
        since 2013.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/nwfilter/nwfilter_driver.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c
index 8e3db43..1a868b6 100644
--- a/src/nwfilter/nwfilter_driver.c
+++ b/src/nwfilter/nwfilter_driver.c
@@ -176,9 +176,6 @@ nwfilterStateInitialize(bool privileged,
     char *base = NULL;
     DBusConnection *sysbus = NULL;
 
-    if (!privileged)
-        return 0;
-
     if (virDBusHasSystemBus() &&
         !(sysbus = virDBusGetSystemBus()))
         return -1;
@@ -193,6 +190,9 @@ nwfilterStateInitialize(bool privileged,
     driver->watchingFirewallD = (sysbus != NULL);
     driver->privileged = privileged;
 
+    if (!privileged)
+        return 0;
+
     nwfilterDriverLock();
 
     if (virNWFilterIPAddrMapInit() < 0)
@@ -535,6 +535,12 @@ nwfilterDefineXML(virConnectPtr conn,
     virNWFilterObjPtr nwfilter = NULL;
     virNWFilterPtr ret = NULL;
 
+    if (!driver->privileged) {
+        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                       _("Can't define NWFilters in session mode"));
+        return NULL;
+    }
+
     nwfilterDriverLock();
     virNWFilterWriteLockFilterUpdates();
     virNWFilterCallbackDriversLock();
-- 
2.0.5