Mercurial > hg
view tests/test-parseindex.t @ 46607:e9901d01d135
revlog: add a mechanism to verify expected file position before appending
If someone uses `hg debuglocks`, or some non-hg process writes to the .hg
directory without respecting the locks, or if the repo's on a networked
filesystem, it's possible for the revlog code to write out corrupted data.
The form of this corruption can vary depending on what data was written and how
that happened. We are in the "networked filesystem" case (though I've had users
also do this to themselves with the "`hg debuglocks`" scenario), and most often
see this with the changelog. What ends up happening is we produce two items
(let's call them rev1 and rev2) in the .i file that have the same linkrev,
baserev, and offset into the .d file, while the data in the .d file is appended
properly. rev2's compressed_size is accurate for rev2, but when we go to
decompress the data in the .d file, we use the offset that's recorded in the
index file, which is the same as rev1, and attempt to decompress
rev2.compressed_size bytes of rev1's data. This usually does not succeed. :)
When using inline data, this also fails, though I haven't investigated why too
closely. This shows up as a "patch decode" error. I believe what's happening
there is that we're basically ignoring the offset field, getting the data
properly, but since baserev != rev, it thinks this is a delta based on rev
(instead of a full text) and can't actually apply it as such.
For now, I'm going to make this an optional component and default it to entirely
off. I may increase the default severity of this in the future, once I've
enabled it for my users and we gain more experience with it. Luckily, most of my
users have a versioned filesystem and can roll back to before the corruption has
been written, it's just a hassle to do so and not everyone knows how (so it's a
support burden). Users on other filesystems will not have that luxury, and this
can cause them to have a corrupted repository that they are unlikely to know how
to resolve, and they'll see this as a data-loss event. Refusing to create the
corruption is a much better user experience.
This mechanism is not perfect. There may be false-negatives (racy writes that
are not detected). There should not be any false-positives (non-racy writes that
are detected as such). This is not a mechanism that makes putting a repo on a
networked filesystem "safe" or "supported", just *less* likely to cause
corruption.
Differential Revision: https://phab.mercurial-scm.org/D9952
author | Kyle Lippincott <spectral@google.com> |
---|---|
date | Wed, 03 Feb 2021 16:33:10 -0800 |
parents | 61e7464477ac |
children | 42d2b31cee0b |
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revlog.parseindex must be able to parse the index file even if an index entry is split between two 64k blocks. The ideal test would be to create an index file with inline data where 64k < size < 64k + 64 (64k is the size of the read buffer, 64 is the size of an index entry) and with an index entry starting right before the 64k block boundary, and try to read it. We approximate that by reducing the read buffer to 1 byte. $ hg init a $ cd a $ echo abc > foo $ hg add foo $ hg commit -m 'add foo' $ echo >> foo $ hg commit -m 'change foo' $ hg log -r 0: changeset: 0:7c31755bf9b5 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: add foo changeset: 1:26333235a41c tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: change foo $ cat >> test.py << EOF > from __future__ import print_function > from mercurial import changelog, node, pycompat, vfs > > class singlebyteread(object): > def __init__(self, real): > self.real = real > > def read(self, size=-1): > if size == 65536: > size = 1 > return self.real.read(size) > > def __getattr__(self, key): > return getattr(self.real, key) > > def __enter__(self): > self.real.__enter__() > return self > > def __exit__(self, *args, **kwargs): > return self.real.__exit__(*args, **kwargs) > > def opener(*args): > o = vfs.vfs(*args) > def wrapper(*a, **kwargs): > f = o(*a, **kwargs) > return singlebyteread(f) > wrapper.options = o.options > return wrapper > > cl = changelog.changelog(opener(b'.hg/store')) > print(len(cl), 'revisions:') > for r in cl: > print(pycompat.sysstr(node.short(cl.node(r)))) > EOF $ "$PYTHON" test.py 2 revisions: 7c31755bf9b5 26333235a41c $ cd .. #if no-pure Test SEGV caused by bad revision passed to reachableroots() (issue4775): $ cd a $ "$PYTHON" <<EOF > from __future__ import print_function > from mercurial import changelog, vfs > cl = changelog.changelog(vfs.vfs(b'.hg/store')) > print('good heads:') > for head in [0, len(cl) - 1, -1]: > print('%s: %r' % (head, cl.reachableroots(0, [head], [0]))) > print('bad heads:') > for head in [len(cl), 10000, -2, -10000, None]: > print('%s:' % head, end=' ') > try: > cl.reachableroots(0, [head], [0]) > print('uncaught buffer overflow?') > except (IndexError, TypeError) as inst: > print(inst) > print('good roots:') > for root in [0, len(cl) - 1, -1]: > print('%s: %r' % (root, cl.reachableroots(root, [len(cl) - 1], [root]))) > print('out-of-range roots are ignored:') > for root in [len(cl), 10000, -2, -10000]: > print('%s: %r' % (root, cl.reachableroots(root, [len(cl) - 1], [root]))) > print('bad roots:') > for root in [None]: > print('%s:' % root, end=' ') > try: > cl.reachableroots(root, [len(cl) - 1], [root]) > print('uncaught error?') > except TypeError as inst: > print(inst) > EOF good heads: 0: [0] 1: [0] -1: [] bad heads: 2: head out of range 10000: head out of range -2: head out of range -10000: head out of range None: an integer is required( .got type NoneType.)? (re) good roots: 0: [0] 1: [1] -1: [-1] out-of-range roots are ignored: 2: [] 10000: [] -2: [] -10000: [] bad roots: None: an integer is required( .got type NoneType.)? (re) $ cd .. Test corrupted p1/p2 fields that could cause SEGV at parsers.c: $ mkdir invalidparent $ cd invalidparent $ hg clone --pull -q --config phases.publish=False ../a limit --config format.sparse-revlog=no $ hg clone --pull -q --config phases.publish=False ../a neglimit --config format.sparse-revlog=no $ hg clone --pull -q --config phases.publish=False ../a segv --config format.sparse-revlog=no $ rm -R limit/.hg/cache neglimit/.hg/cache segv/.hg/cache $ "$PYTHON" <<EOF > data = open("limit/.hg/store/00changelog.i", "rb").read() > poisons = [ > (b'limit', b'\0\0\0\x02'), > (b'neglimit', b'\xff\xff\xff\xfe'), > (b'segv', b'\0\x01\0\0'), > ] > for n, p in poisons: > # corrupt p1 at rev0 and p2 at rev1 > d = data[:24] + p + data[28:127 + 28] + p + data[127 + 32:] > open(n + b"/.hg/store/00changelog.i", "wb").write(d) > EOF $ hg -R limit debugrevlogindex -f1 -c rev flag size link p1 p2 nodeid 0 0000 62 0 2 -1 7c31755bf9b5 1 0000 65 1 0 2 26333235a41c $ hg -R limit debugdeltachain -c rev chain# chainlen prev delta size rawsize chainsize ratio lindist extradist extraratio 0 1 1 -1 base 63 62 63 1.01613 63 0 0.00000 1 2 1 -1 base 66 65 66 1.01538 66 0 0.00000 $ hg -R neglimit debugrevlogindex -f1 -c rev flag size link p1 p2 nodeid 0 0000 62 0 -2 -1 7c31755bf9b5 1 0000 65 1 0 -2 26333235a41c $ hg -R segv debugrevlogindex -f1 -c rev flag size link p1 p2 nodeid 0 0000 62 0 65536 -1 7c31755bf9b5 1 0000 65 1 0 65536 26333235a41c $ hg -R segv debugdeltachain -c rev chain# chainlen prev delta size rawsize chainsize ratio lindist extradist extraratio 0 1 1 -1 base 63 62 63 1.01613 63 0 0.00000 1 2 1 -1 base 66 65 66 1.01538 66 0 0.00000 $ cat <<EOF > test.py > from __future__ import print_function > import sys > from mercurial import changelog, pycompat, vfs > cl = changelog.changelog(vfs.vfs(pycompat.fsencode(sys.argv[1]))) > n0, n1 = cl.node(0), cl.node(1) > ops = [ > ('reachableroots', > lambda: cl.index.reachableroots2(0, [1], [0], False)), > ('compute_phases_map_sets', lambda: cl.computephases({1: {cl.node(0)}})), > ('index_headrevs', lambda: cl.headrevs()), > ('find_gca_candidates', lambda: cl.commonancestorsheads(n0, n1)), > ('find_deepest', lambda: cl.ancestor(n0, n1)), > ] > for l, f in ops: > print(l + ':', end=' ') > try: > f() > print('uncaught buffer overflow?') > except ValueError as inst: > print(inst) > EOF $ "$PYTHON" test.py limit/.hg/store reachableroots: parent out of range compute_phases_map_sets: parent out of range index_headrevs: parent out of range find_gca_candidates: parent out of range find_deepest: parent out of range $ "$PYTHON" test.py neglimit/.hg/store reachableroots: parent out of range compute_phases_map_sets: parent out of range index_headrevs: parent out of range find_gca_candidates: parent out of range find_deepest: parent out of range $ "$PYTHON" test.py segv/.hg/store reachableroots: parent out of range compute_phases_map_sets: parent out of range index_headrevs: parent out of range find_gca_candidates: parent out of range find_deepest: parent out of range $ cd .. #endif