Commit 359be1c8 authored by Jon Dufresne's avatar Jon Dufresne Committed by Tim Graham
Browse files

Fixed #26691 -- Removed checking for a file's existence before deleting. 

File operations always raise a ENOENT error when a file doesn't exist.
Checking the file exists before the operation adds a race condition
condition where the file could be removed between operations. As the
operation already raises an error on a missing file, avoid this race and
avoid checking the file exists twice. Instead only check a file exists
by catching the ENOENT error.
parent e3877c53

django/core/cache/backends/filebased.py

+7 −8
Original line number Diff line number Diff line
@@ -35,14 +35,13 @@ class FileBasedCache(BaseCache): 


    def get(self, key, default=None, version=None):

        fname = self._key_to_file(key, version)

        if os.path.exists(fname):

        try:

            with io.open(fname, 'rb') as f:

                if not self._is_expired(f):

                    return pickle.loads(zlib.decompress(f.read()))

        except IOError as e:

            if e.errno == errno.ENOENT:

                    pass  # Cache file was removed after the exists check

                pass  # Cache file doesn't exist.

        return default



    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):

django/core/files/storage.py

+7 −9
Original line number Diff line number Diff line
@@ -380,10 +380,8 @@ class FileSystemStorage(Storage): 
        assert name, "The name argument is not allowed to be empty."

        name = self.path(name)

        # If the file exists, delete it from the filesystem.

        # Note that there is a race between os.path.exists and os.remove:

        # if os.remove fails with ENOENT, the file was removed

        # concurrently, and we can continue normally.

        if os.path.exists(name):

        # If os.remove() fails with ENOENT, the file may have been removed

        # concurrently, and it's safe to continue normally.

        try:

            os.remove(name)

        except OSError as e:

tests/staticfiles_tests/storage.py

+5 −6
Original line number Diff line number Diff line
@@ -48,7 +48,6 @@ class PathNotImplementedStorage(storage.Storage): 


    def delete(self, name):

        name = self._path(name)

        if os.path.exists(name):

        try:

            os.remove(name)

        except OSError as e: