read_dmi_data: always return None when inside a container.

This fixes stacktrace and warning message that would be printed
to the log if running inside a container and read_dmi_data tried
to access a key that was not present.

In a container, the /sys/class/dmi/id data is not relevant to the
but to the host.  Additionally an unpriviledged container might see
strange behavior:
   # cd /sys/class/dmi/id/
   # id -u
   0
   # ls -l chassis_serial
   -r-------- 1 nobody nogroup 4096 Jun 29 16:49 chassis_serial
   # cat chassis_serial
   cat: /sys/class/dmi/id/chassis_serial: Permission denied

The solution here is to just always return None when running in a
container.

LP: #1701325

1 files changed, 7 insertions, 0 deletions

diff --git a/cloudinit/util.py b/cloudinit/util.py
index c93b6d7e..b486e182 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -2397,6 +2397,10 @@ def read_dmi_data(key):
     """
     Wrapper for reading DMI data.
 
+    If running in a container return None.  This is because DMI data is
+    assumed to be not useful in a container as it does not represent the
+    container but rather the host.
+
     This will do the following (returning the first that produces a
     result):
         1) Use a mapping to translate `key` from dmidecode naming to
@@ -2407,6 +2411,9 @@ def read_dmi_data(key):
     If all of the above fail to find a value, None will be returned.
     """
 
+    if is_container():
+        return None
+
     syspath_value = _read_dmi_syspath(key)
     if syspath_value is not None:
         return syspath_value