RFR: 8304685: heap-buffer-overflow in libjdwp

[Chris Plummer]

On Fri, 12 May 2023 18:32:35 GMT, Kevin Walls <kevinw at openjdk.org> wrote:

> Problem call to skipWhitespace in dbgsysExec src/jdk.jdwp.agent/unix/native/libjdwp/exec_md.c:91
> 
> We call skipWhitespace even when the loop will terminate, should guard against the last skipWhitespace call on the last iteration.
> 
> Could be done differently with the skipWhitespace call at the start of the loop, but skipped on the first iteration, but leaving the statements in the loop in the same order seems more readable.

src/jdk.jdwp.agent/unix/native/libjdwp/exec_md.c line 93:

> 91:         if ((i + 1) == argc) {
> 92:             break; // finished: do not call skipWhitespace again
> 93:         }

It seems a bit odd, because you are breaking out of the middle of the loop by using a breakout condition that is already in the `for` statement, and now serves no purpose. I think I like the idea of moving `skipWhitespace(p)` to the start of the loop. No need to skip in on the first iteration. It will just return p.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13964#discussion_r1192736974