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process_file: avoid race condition: stat data vs. content

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always open the file and then do all operations with the fd:
- fstat
- read
- get xattrs, acls, bsdflags
This commit is contained in:
Thomas Waldmann 2018-08-12 04:50:27 +02:00
parent dca04ba538
commit 677102f292
1 changed files with 49 additions and 49 deletions
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98
src/borg/archive.py
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@ -1126,60 +1126,60 @@ def process_stdin(self, path, cache):
def process_file(self, path, st, cache):
with self.create_helper(path, st, None) as (item, status, hardlinked, hardlink_master): # no status yet
md = None
is_special_file = is_special(st.st_mode)
if not hardlinked or hardlink_master:
if not is_special_file:
path_hash = self.key.id_hash(safe_encode(os.path.join(self.cwd, path)))
known, ids = cache.file_known_and_unchanged(path_hash, st)
else:
# in --read-special mode, we may be called for special files.
# there should be no information in the cache about special files processed in
# read-special mode, but we better play safe as this was wrong in the past:
path_hash = None
known, ids = False, None
chunks = None
if ids is not None:
# Make sure all ids are available
for id_ in ids:
if not cache.seen_chunk(id_):
status = 'M' # cache said it is unmodified, but we lost a chunk: process file like modified
break
with backup_io('open'):
fd = Archive._open_rb(path)
try:
with backup_io('fstat'):
curr_st = os.fstat(fd)
# XXX do some checks here: st vs. curr_st
assert stat.S_ISREG(curr_st.st_mode)
# make sure stats refer to same object that we are processing below
st = curr_st
is_special_file = is_special(st.st_mode)
if not hardlinked or hardlink_master:
if not is_special_file:
path_hash = self.key.id_hash(safe_encode(os.path.join(self.cwd, path)))
known, ids = cache.file_known_and_unchanged(path_hash, st)
else:
chunks = [cache.chunk_incref(id_, self.stats) for id_ in ids]
status = 'U' # regular file, unchanged
else:
status = 'M' if known else 'A' # regular file, modified or added
item.hardlink_master = hardlinked
item.update(self.metadata_collector.stat_simple_attrs(st))
# Only chunkify the file if needed
if chunks is not None:
item.chunks = chunks
else:
with backup_io('open'):
fh = Archive._open_rb(path)
try:
self.process_file_chunks(item, cache, self.stats, self.show_progress, backup_io_iter(self.chunker.chunkify(None, fh)))
md = self.metadata_collector.stat_attrs(st, path, fd=fh)
finally:
os.close(fh)
# in --read-special mode, we may be called for special files.
# there should be no information in the cache about special files processed in
# read-special mode, but we better play safe as this was wrong in the past:
path_hash = None
known, ids = False, None
chunks = None
if ids is not None:
# Make sure all ids are available
for id_ in ids:
if not cache.seen_chunk(id_):
status = 'M' # cache said it is unmodified, but we lost a chunk: process file like modified
break
else:
chunks = [cache.chunk_incref(id_, self.stats) for id_ in ids]
status = 'U' # regular file, unchanged
else:
status = 'M' if known else 'A' # regular file, modified or added
item.hardlink_master = hardlinked
item.update(self.metadata_collector.stat_simple_attrs(st))
# Only chunkify the file if needed
if chunks is not None:
item.chunks = chunks
else:
with backup_io('read'):
self.process_file_chunks(item, cache, self.stats, self.show_progress, backup_io_iter(self.chunker.chunkify(None, fd)))
if not is_special_file:
# we must not memorize special files, because the contents of e.g. a
# block or char device will change without its mtime/size/inode changing.
cache.memorize_file(path_hash, st, [c.id for c in item.chunks])
self.stats.nfiles += 1
if md is None:
fh = Archive._open_rb(path)
try:
md = self.metadata_collector.stat_attrs(st, path, fd=fh)
finally:
os.close(fh)
item.update(md)
item.get_size(memorize=True)
if is_special_file:
# we processed a special file like a regular file. reflect that in mode,
# so it can be extracted / accessed in FUSE mount like a regular file:
item.mode = stat.S_IFREG | stat.S_IMODE(item.mode)
self.stats.nfiles += 1
md = self.metadata_collector.stat_attrs(st, path, fd=fd)
item.update(md)
item.get_size(memorize=True)
if is_special_file:
# we processed a special file like a regular file. reflect that in mode,
# so it can be extracted / accessed in FUSE mount like a regular file:
item.mode = stat.S_IFREG | stat.S_IMODE(item.mode)
finally:
os.close(fd)
return status