RFR(XXS): 8144197: Possible use after free in Arguments::add_property function

[Dmitry Dmitriev]

Hello,

Please, review this small fix. JDK-8132725 removes memory leak in 
Arguments::add_property function in 
hotspot/src/share/vm/runtime/arguments.cpp module, but introduce 
theoretical possibility of use after free of _java_command, because 
_java_command used in reporting OOM errors. This can happen if 
sun.java.command property is defined more than once and JVM can not 
allocate memory for new java command when processing second(or later) 
"sun.java.command" property. Thus sun.java.command can point to the 
freed memory when reporting OOM error, because memory for 
sun.java.command is freed before allocating new sun.java.command. Fix is 
simple - free old sun.java.command only after allocating memory for the 
new one. The similar thing is done for java.vendor.url.bug property in 
case if fatal error occurred during allocation of new 
java.vendor.url.bug property.

JBS: https://bugs.openjdk.java.net/browse/JDK-8144197
webrev.00: http://cr.openjdk.java.net/~ddmitriev/8144197/webrev.00/ 
<http://cr.openjdk.java.net/%7Eddmitriev/8144197/webrev.00/>
Testing: locally, JPRT

Thanks,
Dmitry