lvmdbusd: Handle arbitrary amounts stdout & stderr

When exec'ing lvm, it's possible to get large amounts of both stdout
and stderr depending on the state of lvm and the size of the lvm
configuration.  If we allow any of the buffers to fill we can end
up deadlocking the process.  Ensure we are handling stdout & stderr
during lvm execution.

Ref. https://bugzilla.redhat.com/show_bug.cgi?id=1966636

Signed-off-by: Tony Asleson <tasleson@redhat.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/daemons/lvmdbusd/utils.py b/daemons/lvmdbusd/utils.py
index 66dfbd691..cc221fc2d 100644
--- a/daemons/lvmdbusd/utils.py
+++ b/daemons/lvmdbusd/utils.py
@@ -14,6 +14,7 @@ import ctypes
 import os
 import string
 import datetime
+from fcntl import fcntl, F_GETFL, F_SETFL
 
 import dbus
 from lvmdbusd import cfg
@@ -681,3 +682,16 @@ def _remove_objects(dbus_objects_rm):
 # Remove dbus objects from main thread
 def mt_remove_dbus_objects(objs):
 	MThreadRunner(_remove_objects, objs).done()
+
+
+# Make stream non-blocking
+def make_non_block(stream):
+	flags = fcntl(stream, F_GETFL)
+	fcntl(stream, F_SETFL, flags | os.O_NONBLOCK)
+
+
+def read_decoded(stream):
+	tmp = stream.read()
+	if tmp:
+		return tmp.decode("utf-8")
+	return ''