Re: [PATCH v2 2/3] fanotify: define struct members to hold response decision context
On Thu 05-05-22 20:34:06, Amir Goldstein wrote:
> One open question I have is what should the kernel do with
'info_type' in
> response it does not understand (in the future when there are possibly more
> different info types). It could just skip it because this should be just
> additional info for introspection (the only mandatory part is in
> fanotify_response, however it could surprise userspace that passed info is
> just getting ignored. To solve this we would have to somewhere report
> supported info types (maybe in fanotify fdinfo in proc). I guess we'll
> cross that bridge when we get to it.
>
> Amir, what do you think?
Regardless if and how we provide a way to enumerate supported info types,
I would prefer to reject (EINVAL) unknown info types.
OK, agreed. I will be also calmer when we do that because then we can be
certain userspace does not pass bogus data for unknown info types.
We can provide a command FAN_RESPONSE_TEST to write a test response
with
FAN_NOFD and some extra info so the program can test if certain info
types are supported.
Hum, that would be an option as well. We don't even need the
FAN_RESPONSE_TEST command, do we? The write to fanotify fd for FAN_NOFD fd
would just perform validation of the response and either accept it (do
nothing) or return EINVAL.
Honza
--
Jan Kara <jack(a)suse.com>
SUSE Labs, CR