Fix a heap corruption when printing specific REG_MULTI_SZ values.

[Hugh McMaster]

On Saturday, 23 April 2016 10:24 PM, Sebastian Lackner wrote:

>On 23.04.2016 11:56, Hugh McMaster wrote:
>> On Saturday, 23 April 2016 3:35 AM, Sebastian Lackner wrote:
>>
>>> The current calculation does not take the terminating \0 into account.
>>
>>> -buffer = HeapAlloc(GetProcessHeap(), 0, tmp_size * 2);
>>> +buffer = HeapAlloc(GetProcessHeap(), 0, tmp_size * 2 + sizeof(WCHAR));
>>
>> Which particular cases cause the heap corruption?
>
>It happens for example with a string like L"\0\0\0\0". After stripping off
>the last two "\0" the allocated memory will have a size of 4 characters,
>but the code below writes 5 characters. You can also test with warn+heap
>after creating such a registry key.

Such a string is invalid on Windows. You can't add it using regedit (the
string is trimmed to a single \0 after closing the dialog editor). It also causes
an error with 'reg add'.

That said, users could potentially modify Wine's user.reg, causing a heap
corruption, so this patch is fine. I'll send a Sign-Off.