Re: Have RESOLVE_* flags superseded AT_* flags for new syscalls?

[Christian Brauner]

On Mon, Mar 02, 2020 at 02:50:03PM +0000, David Howells wrote:
> Christian Brauner <christian.brauner@xxxxxxxxxx> wrote:
> 
> > I think we settled this and can agree on RESOLVE_NO_SYMLINKS being the
> > right thing to do, i.e. not resolving symlinks will stay opt-in.
> > Or is your worry even with the current semantics of openat2()? I don't
> > see the issue since O_NOFOLLOW still works with openat2().
> 
> Say, for example, my home dir is on a network volume somewhere and /home has a
> symlink pointing to it.  RESOLVE_NO_SYMLINKS cannot be used to access a file
> inside my homedir if the pathwalk would go through /home/dhowells - this would
> affect fsinfo() - so RESOLVE_NO_SYMLINKS is not a substitute for
> AT_SYMLINK_NOFOLLOW (O_NOFOLLOW would not come into it).

I think we didn't really have this issue/face that question because
openat() never supported AT_SYMLINK_{NO}FOLLOW. Whereas e.g. fsinfo()
does. So in such cases we are back to: either allow both AT_* and
RESOLVE_* flags (imho not the best option) or add (a) new RESOLVE_*
variant(s). It seems we leaned toward the latter so far...

Christian