RFR JDK-8008972

[John Zavgren]

All:
I have a revised webrev image that's ready for review:
http://cr.openjdk.java.net/~jzavgren/8008972/webrev.04/

Thanks
John

On 05/13/2013 04:14 PM, John Zavgren wrote:
> Greetings:
> I posted a new webrev image:
> http://cr.openjdk.java.net/~jzavgren/8008972/webrev.03/
> that fixes a memory leak.
>
> The leak in 
> src/windows/native/java/net/DualStackPlainDatagramSocketImpl.c is 
> caused  by an unfortunate interplay between two actions:
> 1.) dynamically allocating a larger packet buffer when the length of 
> an incoming packet exceeds MAX_BUFFER_LEN.
> 2.) truncating a received packet so that it's length equals 
> MAX_PACKET_LEN, when it exceeds this value.
>
> Action number two was embedded inside the code that implemented action 
> number one, and action number two can change the length of the packet. 
> Unfortunately, the original packet length was used as an indication 
> that the packet buffer needed to be freed, and because the length of 
> the packet may have changed after the allocation, the free() statement 
> wasn't being executed in some cases.
>
> I fixed the problem by moving action number two so that it always 
> precedes action number 1. This ensures that the packet length retains 
> the same value across the malloc() and the free() operations, and 
> therefore packet length can now be used as a reliable indication that 
> dynamically allocated memory must be freed.
>
> I also noticed that there is a procedure in 
> src/windows/native/java/net/TwoStacksPlainDatagramSocketImpl.c that 
> also dynamically allocates memory in a similar way, but it doesn't 
> implement action number two. I added it.
>
> I also took advantage of this opportunity to fix spelling errors in 
> other files in the same directory as the two previously mentioned files.
>
>
> On 03/04/2013 01:17 PM, Chris Hegarty wrote:
>> On 03/04/2013 04:28 PM, John Zavgren wrote:
>>> Greetings:
>>>
>>> I've posted a webrev image of a memory leak fix:
>>> http://cr.openjdk.java.net/~jzavgren/8008972/webrev.01/
>>
>> Sorry John, I don't see what the problem is that you are trying to 
>> solve? Can you please explain why the original code has problems?
>>
>> Also, note that there are other places in the same function that do 
>> the very same check.
>>
>> -Chris.
>>
>>>
>>> Thanks!
>>> John
>>>
>
>

-- 
John Zavgren
john.zavgren at oracle.com
603-821-0904
US-Burlington-MA