So are we saying that WebDav is wrong? I don't see how it is correct to navigate through a folder that you don't have permissions to read.

If we are tempted to go the other way CIFS (and ftp for that matter) can't work without access to details of the parent folder so to make it work would require showing a folder for which you don't have read permissions. I think there's a minefield if we choose that way. The specs may not be explicit about this (because they don't consider implementation details) but its pretty much ingrained in most filesystems.

Do we need to worry about this? What's the problem we are trying to solve?

In a Linux file system, if you have 'x' permission on a directory, you can "cd" into that directory and get to its children (provided you have access to the children of course). However, if you don't have 'r' permission on that same directory, you will not be able to list that directory contents (e.g. doing 'ls -la' will give you nothing). The Unix 'x' permission for a folder is exactly like what we need here: "to be able to traverse to a child folder where you have access, but not be able do listing on the parent folder where you don't have read access".

Yes - we could consider something like UNIX's X permission for a folder - but its not part of the product at the moment and it has wide ranging implications. Another option may be to change the way files are mounted so a user can select which files are mounted and where - possibly controlling the mapping themselves.

I've just seen a recently opened jira (ALF-12967) that concern share and ancestor access permissions. That is a similar problem. So there's an opportunity to fix more than just the filesystem permissions.