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453163d842
be possible to provoke unbounded recursion now, but leaving that to someone else to provoke and repair. Bugfix candidate -- although this is getting harder to backstitch, and the cases it's protecting against are mondo contrived.
285 lines
8.2 KiB
Python
285 lines
8.2 KiB
Python
from test_support import verbose, TESTFN
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import random
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import os
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# From SF bug #422121: Insecurities in dict comparison.
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# Safety of code doing comparisons has been an historical Python weak spot.
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# The problem is that comparison of structures written in C *naturally*
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# wants to hold on to things like the size of the container, or "the
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# biggest" containee so far, across a traversal of the container; but
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# code to do containee comparisons can call back into Python and mutate
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# the container in arbitrary ways while the C loop is in midstream. If the
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# C code isn't extremely paranoid about digging things out of memory on
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# each trip, and artificially boosting refcounts for the duration, anything
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# from infinite loops to OS crashes can result (yes, I use Windows <wink>).
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#
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# The other problem is that code designed to provoke a weakness is usually
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# white-box code, and so catches only the particular vulnerabilities the
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# author knew to protect against. For example, Python's list.sort() code
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# went thru many iterations as one "new" vulnerability after another was
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# discovered.
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#
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# So the dict comparison test here uses a black-box approach instead,
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# generating dicts of various sizes at random, and performing random
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# mutations on them at random times. This proved very effective,
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# triggering at least six distinct failure modes the first 20 times I
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# ran it. Indeed, at the start, the driver never got beyond 6 iterations
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# before the test died.
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# The dicts are global to make it easy to mutate tham from within functions.
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dict1 = {}
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dict2 = {}
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# The current set of keys in dict1 and dict2. These are materialized as
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# lists to make it easy to pick a dict key at random.
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dict1keys = []
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dict2keys = []
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# Global flag telling maybe_mutate() wether to *consider* mutating.
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mutate = 0
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# If global mutate is true, consider mutating a dict. May or may not
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# mutate a dict even if mutate is true. If it does decide to mutate a
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# dict, it picks one of {dict1, dict2} at random, and deletes a random
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# entry from it; or, more rarely, adds a random element.
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def maybe_mutate():
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global mutate
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if not mutate:
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return
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if random.random() < 0.5:
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return
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if random.random() < 0.5:
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target, keys = dict1, dict1keys
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else:
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target, keys = dict2, dict2keys
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if random.random() < 0.2:
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# Insert a new key.
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mutate = 0 # disable mutation until key inserted
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while 1:
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newkey = Horrid(random.randrange(100))
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if newkey not in target:
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break
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target[newkey] = Horrid(random.randrange(100))
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keys.append(newkey)
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mutate = 1
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elif keys:
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# Delete a key at random.
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i = random.randrange(len(keys))
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key = keys[i]
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del target[key]
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# CAUTION: don't use keys.remove(key) here. Or do <wink>. The
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# point is that .remove() would trigger more comparisons, and so
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# also more calls to this routine. We're mutating often enough
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# without that.
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del keys[i]
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# A horrid class that triggers random mutations of dict1 and dict2 when
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# instances are compared.
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class Horrid:
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def __init__(self, i):
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# Comparison outcomes are determined by the value of i.
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self.i = i
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# An artificial hashcode is selected at random so that we don't
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# have any systematic relationship between comparison outcomes
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# (based on self.i and other.i) and relative position within the
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# hash vector (based on hashcode).
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self.hashcode = random.randrange(1000000000)
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def __hash__(self):
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return self.hashcode
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def __cmp__(self, other):
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maybe_mutate() # The point of the test.
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return cmp(self.i, other.i)
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def __repr__(self):
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return "Horrid(%d)" % self.i
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# Fill dict d with numentries (Horrid(i), Horrid(j)) key-value pairs,
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# where i and j are selected at random from the candidates list.
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# Return d.keys() after filling.
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def fill_dict(d, candidates, numentries):
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d.clear()
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for i in xrange(numentries):
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d[Horrid(random.choice(candidates))] = \
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Horrid(random.choice(candidates))
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return d.keys()
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# Test one pair of randomly generated dicts, each with n entries.
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# Note that dict comparison is trivial if they don't have the same number
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# of entires (then the "shorter" dict is instantly considered to be the
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# smaller one, without even looking at the entries).
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def test_one(n):
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global mutate, dict1, dict2, dict1keys, dict2keys
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# Fill the dicts without mutating them.
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mutate = 0
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dict1keys = fill_dict(dict1, range(n), n)
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dict2keys = fill_dict(dict2, range(n), n)
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# Enable mutation, then compare the dicts so long as they have the
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# same size.
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mutate = 1
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if verbose:
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print "trying w/ lengths", len(dict1), len(dict2),
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while dict1 and len(dict1) == len(dict2):
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if verbose:
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print ".",
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c = cmp(dict1, dict2)
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if verbose:
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print
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# Run test_one n times. At the start (before the bugs were fixed), 20
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# consecutive runs of this test each blew up on or before the sixth time
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# test_one was run. So n doesn't have to be large to get an interesting
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# test.
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# OTOH, calling with large n is also interesting, to ensure that the fixed
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# code doesn't hold on to refcounts *too* long (in which case memory would
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# leak).
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def test(n):
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for i in xrange(n):
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test_one(random.randrange(1, 100))
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# See last comment block for clues about good values for n.
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test(100)
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##########################################################################
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# Another segfault bug, distilled by Michael Hudson from a c.l.py post.
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class Child:
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def __init__(self, parent):
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self.__dict__['parent'] = parent
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def __getattr__(self, attr):
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self.parent.a = 1
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self.parent.b = 1
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self.parent.c = 1
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self.parent.d = 1
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self.parent.e = 1
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self.parent.f = 1
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self.parent.g = 1
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self.parent.h = 1
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self.parent.i = 1
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return getattr(self.parent, attr)
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class Parent:
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def __init__(self):
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self.a = Child(self)
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# Hard to say what this will print! May vary from time to time. But
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# we're specifically trying to test the tp_print slot here, and this is
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# the clearest way to do it. We print the result to a temp file so that
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# the expected-output file doesn't need to change.
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f = open(TESTFN, "w")
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print >> f, Parent().__dict__
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f.close()
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os.unlink(TESTFN)
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##########################################################################
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# And another core-dumper from Michael Hudson.
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dict = {}
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# Force dict to malloc its table.
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for i in range(1, 10):
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dict[i] = i
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f = open(TESTFN, "w")
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class Machiavelli:
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def __repr__(self):
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dict.clear()
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# Michael sez: "doesn't crash without this. don't know why."
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# Tim sez: "luck of the draw; crashes with or without for me."
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print >> f
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return `"machiavelli"`
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def __hash__(self):
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return 0
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dict[Machiavelli()] = Machiavelli()
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print >> f, str(dict)
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f.close()
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os.unlink(TESTFN)
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del f, dict
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##########################################################################
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# And another core-dumper from Michael Hudson.
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dict = {}
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# let's force dict to malloc its table
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for i in range(1, 10):
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dict[i] = i
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class Machiavelli2:
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def __eq__(self, other):
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dict.clear()
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return 1
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def __hash__(self):
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return 0
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dict[Machiavelli2()] = Machiavelli2()
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try:
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dict[Machiavelli2()]
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except KeyError:
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pass
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del dict
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##########################################################################
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# And another core-dumper from Michael Hudson.
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dict = {}
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# let's force dict to malloc its table
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for i in range(1, 10):
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dict[i] = i
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class Machiavelli3:
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def __init__(self, id):
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self.id = id
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def __eq__(self, other):
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if self.id == other.id:
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dict.clear()
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return 1
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else:
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return 0
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def __repr__(self):
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return "%s(%s)"%(self.__class__.__name__, self.id)
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def __hash__(self):
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return 0
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dict[Machiavelli3(1)] = Machiavelli3(0)
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dict[Machiavelli3(2)] = Machiavelli3(0)
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f = open(TESTFN, "w")
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try:
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try:
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print >> f, dict[Machiavelli3(2)]
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except KeyError:
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pass
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finally:
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f.close()
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os.unlink(TESTFN)
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del dict
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