Re: [PATCH] vfs: hard-ban creating files with control characters in the name

[Matthew Wilcox]

On Fri, Oct 06, 2017 at 01:09:42PM +1100, Dave Chinner wrote:
> On Thu, Oct 05, 2017 at 12:16:19PM -0400, J. Bruce Fields wrote:
> > This kind of restriction sounds more like a permanent feature of the
> > filesystem--something you'd set at mkfs time.
> > 
> > We already have filesystems with these kinds of restrictions, don't we?
> 
> In general, no. Filename storage typically defined  in the
> filesystem on-disk formats as an opaque string of bytes - the
> filesystem has no business parsing them to determine validity of the
> bytes. Think encrypted filenames and the like - control characters
> in the on-disk format are most definitely necessary and therefore
> must be legal.

Umm.  But filenames still can't have / or \0 in them, so your encryption
already has to avoid at least two special characters.

I agree with your main point though; there is no advantage to doing this
in each individual filesystem.