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Date:   Wed, 9 Sep 2020 18:13:16 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= <mic@digikod.net>
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Subject: Re: [RFC PATCH v8 0/3] Add support for AT_INTERPRETED (was O_MAYEXEC)
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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*.