Fix a corner case when open() fails w/ NXIO/OPNOTSUPP on reg file

Closes: https://github.com/projg2/gemato/issues/21
Signed-off-by: Michał Górny <mgorny@gentoo.org>

2 files changed, 16 insertions, 0 deletions

diff --git a/gemato/verify.py b/gemato/verify.py
index 8e6cbd1..05e568d 100644
--- a/gemato/verify.py
+++ b/gemato/verify.py
@@ -43,6 +43,7 @@ def get_file_metadata(path, hashes):
     StopIteration, or close it explicitly.
     """
 
+    open_exc = None
     try:
         # we want O_NONBLOCK to avoid blocking when opening pipes
         fd = os.open(path, os.O_RDONLY | os.O_NONBLOCK)
@@ -55,6 +56,7 @@ def get_file_metadata(path, hashes):
             # EOPNOTSUPP = opening UNIX socket on FreeBSD
             exists = True
             opened = False
+            open_exc = err
         else:
             raise
     else:
@@ -74,6 +76,10 @@ def get_file_metadata(path, hashes):
         else:
             st = os.stat(path)
 
+        # safety check: if open() failed, it should not be a regular file
+        if not opened and stat.S_ISREG(st.st_mode):
+            raise open_exc
+
         # 2. st_dev
         yield st.st_dev
 
diff --git a/tests/test_verify.py b/tests/test_verify.py
index 8890e1a..0c3fba9 100644
--- a/tests/test_verify.py
+++ b/tests/test_verify.py
@@ -4,11 +4,13 @@
 # Licensed under the terms of 2-clause BSD license
 
 import contextlib
+import errno
 import itertools
 import os
 import os.path
 import socket
 import stat
+import unittest.mock
 
 import pytest
 
@@ -560,3 +562,11 @@ def test_entry_compatibility(a_cls, a_name, a_args, b_cls, b_name,
     e1 = new_manifest_entry(a_cls, a_name, *a_args)
     e2 = new_manifest_entry(b_cls, b_name, *b_args)
     assert verify_entry_compatibility(e1, e2) == (expected, diff)
+
+
+def test_get_file_metadata_fail_to_open_reg(test_tree):
+    """Regression test for when open() fails on a seemingly regular file"""
+    with unittest.mock.patch("os.open") as mock_open:
+        mock_open.side_effect = OSError(errno.ENXIO, "mocked error")
+        with pytest.raises(OSError):
+            list(get_file_metadata(test_tree / "regular-file", {}))