RFR: 8299340: CreateProcessW lpCommandLine must be mutable

[Roger Riggs]

On Fri, 12 May 2023 17:56:08 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>> Launching of processes on Windows using `ProcessCreateW` with a Unicode character set requires the buffer to be writable. An access violation might occur if `ProcessCreateW` writes to the command line string. The current implementation fetches the command line string using JNI GetStringChars returning a buffer that should not be modified. The code is unchanged since 2015.  There have not been any reported faults in that time.
>> 
>> This change copies the command line to a separately allocation mutable buffer to satisfy the Windows requirement.
>
> src/java.base/windows/native/libjava/ProcessImpl_md.c line 385:
> 
>> 383:                         // Copy command line to mutable char buffer; CreateProcessW may modify it
>> 384:                         jsize cmdLen = (*env)->GetStringLength(env, cmd);
>> 385:                         WCHAR *pcmdCopy = (WCHAR*)malloc(cmdLen * sizeof(WCHAR));
> 
> Should this include null terminator, as it is interpreted as `LPWSTR` which is null-terminated?

It seems like it should now.  Java strings are not null terminated and any null termination would have accidental.
But it has worked for a long time (2013) without explicit Unicode null termination.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13894#discussion_r1192685105