Theoretical data race on java.util.logging.Handler.sealed
peter.levart at gmail.com
Tue Dec 3 08:51:56 UTC 2013
While browsing the code of java.util.logging.Handler, I noticed a
theoretical possibility that a security check in a j.u.l.StreamHandler
be circumvented using a data race.
There is a plain boolean instance field 'sealed' in j.u.l.Handler that
is pre-initialized to 'true' in field initializer. StreamHandler
sublcass' constructors overwrite this value with 'false' at the
beginning, then issue some operations which circumvent security checks,
and finally they reset the 'sealed' value back to 'true' at the end.
If a reference to an instance of StreamHandler or subclass is passed to
some thread without synchronization via data-race, this thread can see
'true' or 'false' as the possible values of 'sealed' variable, thus it
is possible to circumvent security checks.
One possibility to fix this is moving the field to StreamHandler and
making it final:
Just making the field volatile might not work. There is an ongoing
debate on concurrency-interest which suggests that volatile fields are
not exceptional in constructors like final fields are...
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