[9] RFR (S): 8175340: Possible invalid memory accesses due to ciMethodData::bci_to_data() returning NULL

[Zoltán Majó]

Thank you for the review, Vladimir!

Best regards,


Zoltan

On 03/09/2017 02:37 AM, Vladimir Kozlov wrote:
> Looks good.
>
> thanks,
> Vladimir
>
> On 3/8/17 1:57 AM, Zoltán Majó wrote:
>> Hi,
>>
>>
>> please review the fix for 8175340.
>>
>> https://bugs.openjdk.java.net/browse/JDK-8175340
>> http://cr.openjdk.java.net/~zmajo/8175340/webrev.01/
>>
>> The method ciMethodData::bci_to_data() can return NULL instead of a 
>> valid ciProfileData*. Some users of the ciProfileData returned by 
>> bci_to_data() do not check if the returned value is NULL, which
>> can result in an invalid memory accesses.
>>
>> The issue has never happened in practice. While working on the issue, 
>> however, I experimented with a VM version that had asserts in 
>> Parse::branch_prediction and to Parse::dynamic_branch_prediction
>> checking that bci_to_data() is not NULL. I was able to trigger some 
>> of the asserts I added by running the VM with -XX:-ProfileInterpreter 
>> -XX:-TieredCompilation. (The asserts are not part of the patch
>> sent out for review.)
>>
>> The fix I propose is simple: Check if bci_to_data() is NULL, if yes, 
>> do not use profiling information / generate profiling code.
>>
>> The fix passes JPRT and RBT testing.
>>
>> Thank you!
>>
>> Best regards,
>>
>>
>> Zoltan
>>