[archive] Handle error when adding /dev/null as a node

Adding /dev/null as a node will trigger EPERM. This can happen namely
when masking systemd units which symlinks to /dev/null. This fix will
avoid a stacktrace and will generate a INFO message about it.

Test for that situation is also included.

Resolves: #893.

Signed-off-by: Louis Bouchard <louis.bouchard@canonical.com>
Signed-off-by: Bryn M. Reeves <bmr@redhat.com>

2 files changed, 15 insertions, 1 deletions

diff --git a/sos/archive.py b/sos/archive.py
index 4d9a4696..463c23b8 100644
--- a/sos/archive.py
+++ b/sos/archive.py
@@ -24,6 +24,7 @@ import shlex
 import re
 import codecs
 import sys
+import errno
 
 # required for compression callout (FIXME: move to policy?)
 from subprocess import Popen, PIPE
@@ -209,7 +210,14 @@ class FileCacheArchive(Archive):
         dest = self.dest_path(path)
         self._check_path(dest)
         if not os.path.exists(dest):
-            os.mknod(dest, mode, device)
+            try:
+                os.mknod(dest, mode, device)
+            except OSError as e:
+                if e.errno == errno.EPERM:
+                    msg = "Operation not permitted"
+                    self.log_info("add_node: %s - mknod '%s'" % (msg, dest))
+                    return
+                raise e
             shutil.copystat(path, dest)
 
     def _makedirs(self, path, mode=0o700):
diff --git a/tests/archive_tests.py b/tests/archive_tests.py
index dac02a04..febc96b4 100644
--- a/tests/archive_tests.py
+++ b/tests/archive_tests.py
@@ -39,6 +39,12 @@ class TarFileArchiveTest(unittest.TestCase):
 
         self.check_for_file('test/tests/ziptest')
 
+    def test_add_node_dev_null(self):
+        st = os.lstat('/dev/null')
+        dev_maj = os.major(st.st_rdev)
+        dev_min = os.minor(st.st_rdev)
+        self.tf.add_node('/dev/null', st.st_mode, os.makedev(dev_maj, dev_min))
+
     # when the string comes from tail() output
     def test_add_string_from_file(self):
         self.copy_strings = []