[ python-Bugs-1517663 ] Interpreter crash: filter() + gc.get_referrers()

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Bugs item #1517663, was opened at 2006-07-05 13:33
Message generated for change (Comment added) made by collinwinter
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Category: Python Interpreter Core
Group: Python 2.5
Status: Open
Resolution: None
Priority: 7
Submitted By: Collin Winter (collinwinter)
Assigned to: Nobody/Anonymous (nobody)
Summary: Interpreter crash: filter() + gc.get_referrers()

Initial Comment:
Similar to the bug in tuple() shown in the current
(r47245) version of Lib/test/crashers/gc_inspection.py,
filter() can be exploited in similar ways.

Rather than the tricky generator used to exploit
tuple(), the attached test case uses a subclass of
tuple with a malicious __getitem__ method. The pattern
being exploited is the same, however: a built-in
function pre-allocates a tuple, then fills it using
calls to user-defined code.

gc_inspection.py.diff also expands the infrastructure
in gc_inspection.py, allowing multiple test functions
to run that could crash the interpreter.

The second patch, fix_filter_crash.patch, is against
Python/bltinmodule.c and adds
_PyObject_GC_TRACK/UNTRACK macros around the call to
the type's sq_item slot in filtertuple().

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>Comment By: Collin Winter (collinwinter)
Date: 2006-07-05 13:54

Message:
Logged In: YES 
user_id=1344176

An alternative fix for this would be not to invoke
filter{tuple,string,unicode} on instances of subclasses of
tuple, str and unicode.

This would fix this bug because you have to be using a
subclass of one of these types to exploit the preallocation.

As a side-effect, this would also resolve the issue I raised
in bug #1517509 concerning filter()'s treatment of these
subtypes re: the iterator protocol.

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