[8] RFR of 8066985: Java Webstart downloading packed files can result in Timezone set to UTC
mikhail cherkasov
mikhail.cherkasov at oracle.com
Wed Mar 25 09:51:11 UTC 2015
On 3/25/2015 1:48 AM, Kumar Srinivasan wrote:
> Hi Mikhail,
>
> Nit:
> Utils.java:
> - // reset timezone when all the packers have terminated
> + // reset timezone when all the packer/unpacker instances have terminated
fixed: http://cr.openjdk.java.net/~mcherkas/8066985/webrev.03/
>
>
> DefaultTimeZoneTest.java
> What did you change between 01 and 02 revisions ? They appear to be the
> same ?
Please, see revisions 00 and 02. 01 has DefaultTimeZoneTest.java.rej, 02
is the same but without this extra file.
>
> Kumar
>
>
> On 3/24/2015 1:14 PM, mikhail cherkasov wrote:
>> Hi there,
>>
>> There's a new webrev:
>> http://cr.openjdk.java.net/~mcherkas/8066985/webrev.02/
>>
>> I reduced the a thread number in the test, because with big count of
>> threads I got OOM on JPRT.
>> And extract common part form PackerImpl and UnpackerImpl to Utils.
>>
>> Thanks,
>> Mikhail.
>>
>>
>> On 3/20/2015 6:04 PM, mikhail cherkasov wrote:
>>>
>>> On 3/19/2015 7:29 PM, Peter Levart wrote:
>>>> On 03/19/2015 04:46 PM, Peter Levart wrote:
>>>>> On 03/19/2015 02:53 PM, Kumar Srinivasan wrote:
>>>>>> Mikhail,
>>>>>>
>>>>>> You can move the common utilitieschangeDefaultTimeZoneToUtc and
>>>>>> restoreDefaultTimeZoneto Utils.java.
>>>>>>
>>>>>> Also I am not sure how effective the test is ? does it catch the
>>>>>> issue ?
>>>>>> if you don't have the fix in PackerImpl and UnpackerImpl ?
>>>>>>
>>>>>> Otherwise it looks good, and I can sponsor this patch for you.
>>>>>>
>>>>>> Kumar
>>>>>
>>>>> Hi Mikhail,
>>>>>
>>>>> Is this code part of some utility so that it is executed
>>>>> exclusively in it's own JVM, or can it also be executed by some
>>>>> public API or internal JVM thread? It appears to be the later
>>>>> (used by java.util.jar.Pack200 public API), but haven't checked.
>>>>>
>>>>> In case of the later, I think it is very strange that the code
>>>>> changes global JVM timezone, albeit just temporarily. This could
>>>>> affect other code that needs default TZ and executes concurrently.
>>>>>
>>>>> Even in case of the former, if the PackerImpl.pack can be executed
>>>>> by multiple concurrent threads and if UnpackerImpl.unpack can be
>>>>> executed by multiple concurrent threads, what guarantees that some
>>>>> PackerImpl.pack thread is not executed concurrently with some
>>>>> UnpackerImpl.unpack thread? You only track each method separately.
>>> Agree, I'll move changeDefaultTimeZoneToUtc and
>>> restoreDefaultTimeZone to Util class, so TZ changes will be managed
>>> in one place for both PackerImpl and UnpackerImpl classes.
>>>
>>> NonPack200 threads that reads/writes DTZ can collide with Pack200,
>>> but there's other bug that should fix this:
>>> https://bugs.openjdk.java.net/browse/JDK-8073187
>>>
>>> My fix is only for jdk8 and 7, and it focused on making
>>> packer/unpacker safe for concurrent use, because now applets and
>>> JNLP uses packer/unpacker concurrently and this can
>>> lead to DTZ changing to UTC.
>>>
>>>>>
>>>>>
>>>>> Regards, Peter
>>>>
>>>> I guess this default TZ manipulation is needed because
>>>> JarOutputStream/JarInputStream don't provide constructors that
>>>> would take a TZ object, but always use default TZ, right?
>>>>
>>>> The cleanest way would be to add such constructors, but if this is
>>>> too much for 8u, then perhaps some internal ThreadLocal<TZ> could
>>>> be exposed to both PackerImpl/UnpackerImpl and
>>>> Jar[Zip]Input[Output] stream internals. It think the use of default
>>>> TZ in Jar/Zip/Streams is very localized. It is needed to convert
>>>> local time (specified as DOS time) to and from epoch-based time
>>>> exposed in ZipEntry. The code is located in package-private class
>>>> java.util.zip.ZipUtils in methods dosToJavaTime /javaToDosTime (or
>>>> equivalent extendedDosToJavaTime / javaToExtendedDosTime in JDK9).
>>> all solutions that you described require introducing a new API and
>>> this can not be done for jdk7 and 8, so that's why JDK-8073187 was
>>> created.
>>> The main purpose of this fix is to make packed jars delivery save
>>> for applets/jnlp application.
>>>
>>>>
>>>> Another way would be to provide a general thread-local default TZ
>>>> override in TimeZone itself. Something like the following:
>>>>
>>>> ===================================================================
>>>> --- jdk/src/share/classes/java/util/TimeZone.java
>>>> +++ jdk/src/share/classes/java/util/TimeZone.java
>>>> @@ -630,8 +630,11 @@
>>>> * method doesn't create a clone.
>>>> */
>>>> static TimeZone getDefaultRef() {
>>>> - TimeZone defaultZone = defaultTimeZone;
>>>> + TimeZone defaultZone = threadLocalTimeZone.get();
>>>> if (defaultZone == null) {
>>>> + defaultZone = defaultTimeZone;
>>>> + }
>>>> + if (defaultZone == null) {
>>>> // Need to initialize the default time zone.
>>>> defaultZone = setDefaultZone();
>>>> assert defaultZone != null;
>>>> @@ -713,6 +716,20 @@
>>>> defaultTimeZone = zone;
>>>> }
>>>>
>>>> + public void withThreadDefaultDo(Runnable runnable) {
>>>> + TimeZone prevZone = threadLocalTimeZone.get();
>>>> + threadLocalTimeZone.set(this);
>>>> + try {
>>>> + runnable.run();
>>>> + } finally {
>>>> + if (prevZone == null) {
>>>> + threadLocalTimeZone.remove();
>>>> + } else {
>>>> + threadLocalTimeZone.set(prevZone);
>>>> + }
>>>> + }
>>>> + }
>>>> +
>>>> /**
>>>> * Returns true if this zone has the same rule and offset as
>>>> another zone.
>>>> * That is, if this zone differs only in ID, if at all.
>>>> Returns false
>>>> @@ -760,6 +777,8 @@
>>>> */
>>>> private String ID;
>>>> private static volatile TimeZone defaultTimeZone;
>>>> + private static final ThreadLocal<TimeZone> threadLocalTimeZone =
>>>> + new ThreadLocal<>();
>>>>
>>>> static final String GMT_ID = "GMT";
>>>> private static final int GMT_ID_LENGTH = 3;
>>>>
>>>>
>>>> Regards, Peter
>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>> On 3/18/2015 3:07 PM, Kumar Srinivasan wrote:
>>>>>>>
>>>>>>> Hello Mikhail,
>>>>>>>
>>>>>>>> Hi all,
>>>>>>>>
>>>>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8066985
>>>>>>>>
>>>>>>>> The problem is that packer/unpacker changes global state(
>>>>>>>> default time zone ) without proper synchronization:
>>>>>>>> http://hg.openjdk.java.net/jdk9/client/jdk/file/a159e5358e25/src/java.base/share/classes/com/sun/java/util/jar/pack/PackerImpl.java#l85
>>>>>>>>
>>>>>>>>
>>>>>>>> however javadoc says that it's save to use it in concurrent way
>>>>>>>> if each thread has it's own packer/unpacker instance:
>>>>>>>> http://hg.openjdk.java.net/jdk9/client/jdk/file/a159e5358e25/src/java.base/share/classes/java/util/jar/Pack200.java#l149
>>>>>>>>
>>>>>>>>
>>>>>>>> The fix is:
>>>>>>>> 1. first packer/unpacker saves default time zone
>>>>>>>> 2. the last set it back.
>>>>>>>>
>>>>>>>> Webrev:
>>>>>>>> http://cr.openjdk.java.net/~mcherkas/8066985/webrev.00/
>>>>>>>
>>>>>>> The above link is wrong!, it takes me to webrev for 8073187,
>>>>>>> which has only the PackerImpl changes.
>>>>>>>
>>>>>>> I am guessing the link should be:
>>>>>>> http://cr.openjdk.java.net/~mcherkas/8066985/webrev.00/
>>>>>>>
>>>>>>> Kumar
>>>>>>>
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Mikhail.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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