Created attachment 14064 [details]
patch to vfs_streams_depot.c
The streams_depot plugin stores alternate data streams in a directory tree based on a hash of the parent file's inode. If two different users create alternate data streams on files that hash to a common parent sub-directory, the second user receives a permission error because the sub-directory is owned by the first user and the mode is set to 0755.
A fix for this is to set the mode to 01777 (with the sticky bit), which still prevents inappropriate deletion of ADS files, but allows anyone to create new ADS files. I've attached a patch with this proposed fix.