File.__iter__() Quadratic-time DoS

[wooseokdotkim]

I thought the code below could generate DoS, so I made a bug report
However, File._iter was not recognized as a bug because only one line was buffered and only worked for chunks returned from File.chunks, but it was determined that verification code for input should be added, so it was created as an open ticket.

The code pattern is similar to CVE-2023-36053, which is already released, so I think it needs to be modified.

code: django/core/files/base.py:89

""
def iter(self):

buffer_ = None
for chunk in self.chunks():

for line in chunk.splitlines(True):

if buffer_:

line = buffer_ + line # < Code!

""

How should I patch it?