hw-mgmt: scripts: Make creation of parsed VPD files atomic

Fix VPD parsing script to create the output file atomically,
so that file always appears complete or not at all.

This ensures that other processes won't see incomplete data.

Bug: 4738257, 4502950, 4499192

Signed-off-by: Felix Radensky <[email protected]>

Author: felixradensky

usr/usr/bin/hw-management-vpd-parser.py

@@ -744,19 +744,37 @@ def save_fru(fru_dict, out_filename):
     @param out_filename: output filename
     @return: None
     """
+    # Get the directory of the output file for the temporary file
+    out_dir = os.path.dirname(out_filename) or '.'
+    tmp_filename = None
+
     try:
-        out_file = open(out_filename, 'w+')
-    except IOError as err:
+        # Create a temporary file in the same directory as the target file
+        # This ensures the rename operation is atomic (same filesystem)
+        with tempfile.NamedTemporaryFile(mode='w', dir=out_dir, delete=False) as tmp_file:
+            tmp_filename = tmp_file.name
+
+            # Write all FRU data to the temporary file
+            for item in fru_dict['items']:
+                if item[0]:
+                    tmp_file.write("{:<25}{}\n".format(item[0] + ":", str(item[1]).rstrip()))
+                else:
+                    tmp_file.write("{}\n".format(str(item[1]).rstrip()))
+
+        # Atomically rename the temporary file to the target filename
+        # On POSIX systems, this is an atomic operation
+        os.replace(tmp_filename, out_filename)
+
+    except (IOError, OSError) as err:
         print("I/O error({0}): {1} with log file {2}".format(err.errno,
                                                              err.strerror,
                                                              out_filename))
-    for item in fru_dict['items']:
-        if item[0]:
-            out_file.write("{:<25}{}\n".format(item[0] + ":", str(item[1]).rstrip()))
-        else:
-            out_file.write("{}\n".format(str(item[1]).rstrip()))
-
-    out_file.close()
+        # Clean up temporary file if it exists
+        if tmp_filename and os.path.exists(tmp_filename):
+            try:
+                os.remove(tmp_filename)
+            except OSError:
+                pass
 
 
 def load_fru_bin(file_name):