RFR JDK-8008972

[John Zavgren]

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