[9] RFR(S): Crash with assert: symbol conversion failure in java_lang_String::create_from_symbol()

David Holmes david.holmes at oracle.com
Mon Sep 12 00:47:46 UTC 2016

On 10/09/2016 6:55 AM, Coleen Phillimore wrote:
> This change is fine because it matches the commented out assert in
> create_from_str().   We should probably figure out what it would take to
> check the characters coming in from JNI and decide whether we should do
> this.  If not, it doesn't make sense to have commented out asserts.
> But this is okay for jdk9.

Grumble, grumble ... both are bad. If the VM doesn't validate this bad 
UTF-8 then where does it go? And how does the generator of the bad UTF-8 
get informed? An assert may be too drastic but can we throw an exception 
(InternalError?) ?


> Thanks,
> Coleen
> On 9/9/16 8:42 AM, Tobias Hartmann wrote:
>> Hi,
>> please review the following patch:
>> https://bugs.openjdk.java.net/browse/JDK-8164561
>> http://cr.openjdk.java.net/~thartmann/8164561/webrev.00/
>> The verification code in java_lang_String::create_from_symbol() that
>> was added by Compact Strings fails because the input symbol does not
>> contain valid UTF8. The problem is that a JCK JNI test passes an
>> invalid UTF8 string as class name to the JNI method "FindClass". In
>> fact, the string contains garbage from reading past array boundaries
>> because of a bug in the test [1]. The JNI spec [2] states that 'name'
>> should be "a fully-qualified class name (that is, a package name,
>> delimited by “/”, followed by the class name). If the name begins with
>> “[“ (the array signature character), it returns an array class. The
>> string is encoded in modified UTF-8".
>> I nevertheless think that we should not crash in the case of an
>> invalid UTF8 string and therefore disabled the verification code with
>> a comment. We did the same for java_lang_String::create_from_str() [3].
>> Tested with failing JCK test and JPRT (running).
>> Thanks,
>> Tobias
>> [1] https://bugs.openjdk.java.net/browse/JCK-7307244
>> [2]
>> https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/functions.html#FindClass
>> [3]
>> http://hg.openjdk.java.net/jdk9/hs/hotspot/file/d060826d0911/src/share/vm/classfile/javaClasses.cpp#l274

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