Fix off-by-one error in udevListInterfacesByStatus

Ever since this function was introduced in 2012 it could've tried
filling in an extra interface name.  That was made worse in 2019 when
the caller functions started accepting NULL arrays of size 0.

This is assigned CVE-2024-1441.

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Reported-by: Alexander Kuznetsov <kuznetsovam@altlinux.org>
Fixes: 5a33366f5c
Fixes: d6064e2759
Reviewed-by: Ján Tomko <jtomko@redhat.com>

NEWS.rst

@@ -13,6 +13,21 @@ v10.1.0 (unreleased)
 
 * **Security**
 
+  * ``CVE-2024-1441``: Fix off-by-one error leading to a crash
+
+    In **libvirt-1.0.0** there were couple of interface listing APIs
+    introduced which had an off-by-one error.  That error could lead to a
+    very rare crash if an array was passed to those functions which did
+    not fit all the interfaces.
+
+    In **libvirt-5.10** a check for non-NULL arrays has been adjusted to
+    allow for NULL arrays with size 0 instead of rejecting all NULL
+    arrays.  However that made the above issue significantly worse since
+    that off-by-one error now did not write beyond an array, but
+    dereferenced said NULL pointer making the crash certain in a
+    specific scenario in which a NULL array of size 0 was passed to the
+    aforementioned functions.
+
 * **Removed features**
 
 * **New features**

src/interface/interface_backend_udev.c

@@ -222,7 +222,7 @@ udevListInterfacesByStatus(virConnectPtr conn,
         g_autoptr(virInterfaceDef) def = NULL;
 
         /* Ensure we won't exceed the size of our array */
-        if (count > names_len)
+        if (count >= names_len)
             break;
 
         path = udev_list_entry_get_name(dev_entry);