Mercurial > hg
view mercurial/cffi/osutil.py @ 40626:87a872555e90
revlog: detect incomplete revlog reads
_readsegment() is supposed to return N bytes of revlog revision
data starting at a file offset. Surprisingly, its behavior before
this patch never verified that it actually read and returned N
bytes! Instead, it would perform the read(), then return whatever
data was available. And even more surprisingly, nothing in the
call chain appears to have been validating that it received all
the data it was expecting.
This behavior could lead to partial or incomplete revision chunks
being operated on. This could result in e.g. cached deltas being
applied against incomplete base revisions. The delta application
process would happily perform this operation. Only hash
verification would detect the corruption and save us.
This commit changes the behavior of raw revlog reading to validate
that we actually read() the number of bytes that were requested.
We will raise a more specific error faster, rather than possibly
have it go undetected or manifest later in the call stack, at
delta application or hash verification.
Differential Revision: https://phab.mercurial-scm.org/D5266
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Tue, 13 Nov 2018 12:30:59 -0800 |
parents | dacfcdd8b94e |
children | 2372284d9457 |
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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("struct timespec", "tv_sec") buf = ffi.new("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("val_attrs_t*", buf) for i in range(r): lgt = cur.length assert lgt == ffi.cast('uint32_t*', cur)[0] ofs = cur.name_info.attr_dataoffset str_lgt = cur.name_info.attr_length base_ofs = ffi.offsetof('val_attrs_t', 'name_info') name = str(ffi.buffer(ffi.cast("char*", cur) + base_ofs + ofs, str_lgt - 1)) tp = attrkinds[cur.obj_type] if name == "." or name == "..": 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("val_attrs_t*", int(ffi.cast("intptr_t", cur)) + lgt) return ret def listdir(path, stat=False, skip=None): req = ffi.new("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