Re: [RFC PATCH v8 0/3] Add support for AT_INTERPRETED (was O_MAYEXEC)

From: Mickaël Salaün
Date: Wed Sep 09 2020 - 13:56:33 EST

On 09/09/2020 19:13, Al Viro wrote:
> On Wed, Sep 09, 2020 at 09:19:11AM +0200, Mickaël Salaün wrote:
>> On 08/09/2020 20:50, Al Viro wrote:
>>> On Tue, Sep 08, 2020 at 09:59:53AM +0200, Mickaël Salaün wrote:
>>>> 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*.

Fine, I'll do it. It will look a lot like this one though.