Possible security bug with unmount

[Cédric Picard]

Hi,

I find that DIR_unmount_device in wine/dlls/ntdll/directory.c (latest
git) is looking like an unsafe use of system().

If a device was mounted to a point such as ";ls" I think it would be
passed to system and cause a command injection.

I didn't open a bug because I wasn't able to really test it due to my
lack of knowledge of wine and because I can't think of a real world
attack based on this as it needs to mount a device first but I think
it's worth at least a thorough check.

Cédric Picard