On Wed, 9 Sep 2020, Al Viro wrote:

On Wed, Sep 09, 2020 at 09:19:11AM +0200, Mickaël Salaün wrote:

quoted

On 08/09/2020 20:50, Al Viro wrote:

quoted

On Tue, Sep 08, 2020 at 09:59:53AM +0200, Mickaël Salaün wrote:

quoted

Hi,

This height patch series rework the previous O_MAYEXEC series by not
adding a new flag to openat2(2) but to faccessat2(2) instead.  As
suggested, this enables to perform the access check on a file descriptor
instead of on a file path (while opening it).  This may require two
checks (one on open and then with faccessat2) but it is a more generic
approach [8].

Again, why is that folded into lookup/open/whatnot, rather than being
an operation applied to a file (e.g. O_PATH one)?

I don't understand your question. AT_INTERPRETED can and should be used
with AT_EMPTY_PATH. The two checks I wrote about was for IMA.

Once more, with feeling: don't hide that behind existing syscalls.
If you want to tell LSM have a look at given fs object in a special
way, *add* *a* *new* *system* *call* *for* *doing* *just* *that*.

It's not just for LSM, though, and it has identical semantics from the 
caller's POV as faccessat().



-- 
James Morris
[off-list ref]