Based on my search, this repository does not contain the Django codebase. However, I can generate the patch based on my knowledge of the Django codebase structure and the issue requirements. The issue is well-documented and I understand what changes need to be made:

1. Change the default value of `FILE_UPLOAD_PERMISSIONS` from `None` to `0o644` in `django/conf/global_settings.py`
2. Update the documentation in settings docs and deployment checklist
3. Add release notes

Here's the patch:

--- a/django/conf/global_settings.py
+++ b/django/conf/global_settings.py
@@ -304,7 +304,7 @@ DEFAULT_FILE_STORAGE = 'django.core.files.storage.FileSystemStorage'
 # File upload permissions
 
 # The numeric mode to set newly-uploaded files to. The value should be a mode
-# you'd pass directly to os.chmod; see https://docs.python.org/library/os.html#files-and-directories.
-FILE_UPLOAD_PERMISSIONS = None
+# you'd pass directly to os.chmod; see https://docs.python.org/library/os.html#files-and-directories.
+FILE_UPLOAD_PERMISSIONS = 0o644
 
 # The numeric mode to apply to directories created in the process of uploading files.
--- a/docs/ref/settings.txt
+++ b/docs/ref/settings.txt
@@ -1737,15 +1737,18 @@ FILE_UPLOAD_PERMISSIONS
 
 Default: ``None``
 
+Default: ``0o644``
+
 The numeric mode (i.e. ``0o644``) to set newly uploaded files to. For
 more information about what these modes mean, see the documentation for
 :func:`os.chmod`.
 
 If this isn't given or is ``None``, you'll get operating-system dependent
-behavior. On most platforms, temporary files will have a mode of ``0o600``,
-and files saved from memory will be saved using the system's standard umask.
+behavior. On most platforms, temporary files will have a mode of ``0o600``, and
+files saved from memory will be saved using the system's standard umask.
 
 .. warning::
 
     **Always prefix the mode with ``0o``.**
 
     If you're not familiar with file modes, please note that the ``0o`` prefix
--- a/docs/howto/deployment/checklist.txt
+++ b/docs/howto/deployment/checklist.txt
@@ -90,10 +90,7 @@ can often be problematic.
 :setting:`FILE_UPLOAD_PERMISSIONS`
 ----------------------------------
 
-If you upload files, ensure that :setting:`FILE_UPLOAD_PERMISSIONS` is
-set to ensure the newly uploaded files don't have overly permissive 
-permissions. In previous versions of Django, this setting was not applied
-and thus file permissions varied depending on the size of the uploaded file.
+The default value (``0o644``) is suitable for most situations.
--- a/docs/releases/3.0.txt
+++ b/docs/releases/3.0.txt
@@ -0,0 +1,15 @@
+Backwards incompatible changes in 3.0
+=====================================
+
+:setting:`FILE_UPLOAD_PERMISSIONS` default changed
+--------------------------------------------------
+
+The default value of :setting:`FILE_UPLOAD_PERMISSIONS` has changed from
+``None`` to ``0o644``. Previously, with the default of ``None``, files
+uploaded via :class:`~django.core.files.uploadedfile.TemporaryUploadedFile`
+would have a mode of ``0o600`` on some operating systems, while files
+uploaded via :class:`~django.core.files.uploadedfile.InMemoryUploadedFile`
+would use the system's standard umask, often resulting in ``0o644``.
+
+To restore the previous behavior, set ``FILE_UPLOAD_PERMISSIONS`` to
+``None`` in your project settings.