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dirs: resolve fuzzer OOM situation by disallowing deep directory hierarchies...
dirs: resolve fuzzer OOM situation by disallowing deep directory hierarchies It seems like 2048 directories ought to be enough for any reasonable use of Mercurial? A previous version of this patch scanned for slashes before any allocations occurred. That approach is slower than this in the happy path, but much faster than this in the case that too many slashes are encountered. We may want to revisit it in the future using memchr() so it'll be well-optimized by the libc we're using. .. bc: Mercurial will now defend against OOMs by refusing to operate on paths with 2048 or more components. This means that _extremely_ deep path hierarchies will be rejected, but we anticipate nobody is using hierarchies this deep. Differential Revision: https://phab.mercurial-scm.org/D7411

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osutil.py
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# osutil.py - CFFI version of osutil.c
#
# Copyright 2016 Maciej Fijalkowski <fijall@gmail.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
import os
import stat as statmod
from ..pure.osutil import *
from .. import pycompat
if pycompat.isdarwin:
from . import _osutil
ffi = _osutil.ffi
lib = _osutil.lib
listdir_batch_size = 4096
# tweakable number, only affects performance, which chunks
# of bytes do we get back from getattrlistbulk
attrkinds = [None] * 20 # we need the max no for enum VXXX, 20 is plenty
attrkinds[lib.VREG] = statmod.S_IFREG
attrkinds[lib.VDIR] = statmod.S_IFDIR
attrkinds[lib.VLNK] = statmod.S_IFLNK
attrkinds[lib.VBLK] = statmod.S_IFBLK
attrkinds[lib.VCHR] = statmod.S_IFCHR
attrkinds[lib.VFIFO] = statmod.S_IFIFO
attrkinds[lib.VSOCK] = statmod.S_IFSOCK
class stat_res(object):
def __init__(self, st_mode, st_mtime, st_size):
self.st_mode = st_mode
self.st_mtime = st_mtime
self.st_size = st_size
tv_sec_ofs = ffi.offsetof(b"struct timespec", b"tv_sec")
buf = ffi.new(b"char[]", listdir_batch_size)
def listdirinternal(dfd, req, stat, skip):
ret = []
while True:
r = lib.getattrlistbulk(dfd, req, buf, listdir_batch_size, 0)
if r == 0:
break
if r == -1:
raise OSError(ffi.errno, os.strerror(ffi.errno))
cur = ffi.cast(b"val_attrs_t*", buf)
for i in range(r):
lgt = cur.length
assert lgt == ffi.cast(b'uint32_t*', cur)[0]
ofs = cur.name_info.attr_dataoffset
str_lgt = cur.name_info.attr_length
base_ofs = ffi.offsetof(b'val_attrs_t', b'name_info')
name = str(
ffi.buffer(
ffi.cast(b"char*", cur) + base_ofs + ofs, str_lgt - 1
)
)
tp = attrkinds[cur.obj_type]
if name == b"." or name == b"..":
continue
if skip == name and tp == statmod.S_ISDIR:
return []
if stat:
mtime = cur.mtime.tv_sec
mode = (cur.accessmask & ~lib.S_IFMT) | tp
ret.append(
(
name,
tp,
stat_res(
st_mode=mode,
st_mtime=mtime,
st_size=cur.datalength,
),
)
)
else:
ret.append((name, tp))
cur = ffi.cast(
b"val_attrs_t*", int(ffi.cast(b"intptr_t", cur)) + lgt
)
return ret
def listdir(path, stat=False, skip=None):
req = ffi.new(b"struct attrlist*")
req.bitmapcount = lib.ATTR_BIT_MAP_COUNT
req.commonattr = (
lib.ATTR_CMN_RETURNED_ATTRS
| lib.ATTR_CMN_NAME
| lib.ATTR_CMN_OBJTYPE
| lib.ATTR_CMN_ACCESSMASK
| lib.ATTR_CMN_MODTIME
)
req.fileattr = lib.ATTR_FILE_DATALENGTH
dfd = lib.open(path, lib.O_RDONLY, 0)
if dfd == -1:
raise OSError(ffi.errno, os.strerror(ffi.errno))
try:
ret = listdirinternal(dfd, req, stat, skip)
finally:
try:
lib.close(dfd)
except BaseException:
pass # we ignore all the errors from closing, not
# much we can do about that
return ret