From 6c83c2710760a4f551d1a925fc9b1a19ae8797c1 Mon Sep 17 00:00:00 2001
From: Sean Quah <8349537+squahtx@users.noreply.github.com>
Date: Mon, 27 Sep 2021 11:29:23 +0100
Subject: [PATCH] Fix race conditions when creating media store and config
 directories (#10913)

---
 changelog.d/10913.bugfix                  | 1 +
 synapse/config/_base.py                   | 9 ++-------
 synapse/rest/media/v1/media_storage.py    | 6 ++----
 synapse/rest/media/v1/storage_provider.py | 3 +--
 4 files changed, 6 insertions(+), 13 deletions(-)
 create mode 100644 changelog.d/10913.bugfix

diff --git a/changelog.d/10913.bugfix b/changelog.d/10913.bugfix
new file mode 100644
index 0000000000..a0015c8241
--- /dev/null
+++ b/changelog.d/10913.bugfix
@@ -0,0 +1 @@
+Fix race conditions when creating media store and config directories.
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index 2cc242782a..d974a1a2a8 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -200,11 +200,7 @@ class Config:
     @classmethod
     def ensure_directory(cls, dir_path):
         dir_path = cls.abspath(dir_path)
-        try:
-            os.makedirs(dir_path)
-        except OSError as e:
-            if e.errno != errno.EEXIST:
-                raise
+        os.makedirs(dir_path, exist_ok=True)
         if not os.path.isdir(dir_path):
             raise ConfigError("%s is not a directory" % (dir_path,))
         return dir_path
@@ -693,8 +689,7 @@ class RootConfig:
                     open_private_ports=config_args.open_private_ports,
                 )
 
-                if not path_exists(config_dir_path):
-                    os.makedirs(config_dir_path)
+                os.makedirs(config_dir_path, exist_ok=True)
                 with open(config_path, "w") as config_file:
                     config_file.write(config_str)
                     config_file.write("\n\n# vim:ft=yaml")
diff --git a/synapse/rest/media/v1/media_storage.py b/synapse/rest/media/v1/media_storage.py
index 01fada8fb5..fca239d8c7 100644
--- a/synapse/rest/media/v1/media_storage.py
+++ b/synapse/rest/media/v1/media_storage.py
@@ -132,8 +132,7 @@ class MediaStorage:
         fname = os.path.join(self.local_media_directory, path)
 
         dirname = os.path.dirname(fname)
-        if not os.path.exists(dirname):
-            os.makedirs(dirname)
+        os.makedirs(dirname, exist_ok=True)
 
         finished_called = [False]
 
@@ -244,8 +243,7 @@ class MediaStorage:
                 return legacy_local_path
 
         dirname = os.path.dirname(local_path)
-        if not os.path.exists(dirname):
-            os.makedirs(dirname)
+        os.makedirs(dirname, exist_ok=True)
 
         for provider in self.storage_providers:
             res: Any = await provider.fetch(path, file_info)
diff --git a/synapse/rest/media/v1/storage_provider.py b/synapse/rest/media/v1/storage_provider.py
index 289e4297f2..da78fcee5e 100644
--- a/synapse/rest/media/v1/storage_provider.py
+++ b/synapse/rest/media/v1/storage_provider.py
@@ -138,8 +138,7 @@ class FileStorageProviderBackend(StorageProvider):
         backup_fname = os.path.join(self.base_directory, path)
 
         dirname = os.path.dirname(backup_fname)
-        if not os.path.exists(dirname):
-            os.makedirs(dirname)
+        os.makedirs(dirname, exist_ok=True)
 
         await defer_to_thread(
             self.hs.get_reactor(), shutil.copyfile, primary_fname, backup_fname