Christophe LEROY <christophe.le...@c-s.fr> writes: > Le 02/06/2017 à 14:11, Benjamin Herrenschmidt a écrit : >> On Fri, 2017-06-02 at 11:39 +0200, Christophe LEROY wrote: >>> The difference between get_user() and __get_user() is that get_user() >>> performs an access_ok() in addition. >>> >>> Doesn't access_ok() only checks whether addr is below TASK_SIZE to >>> ensure it is a valid user address ? >> >> Do you have a measurable improvement by skipping that check ? I agree >> with your reasoning but I'm also paranoid and so I wouldn't change it >> unless it's really worth it. >> > > No I don't have. Taking into account the patch following this serie > which limits even more the calls to get_user(), it is probably not worth > it anymore (see https://patchwork.ozlabs.org/patch/757564/) > > I will then have to resubmit the entire serie (including that additional > one), but there is no get_user_inatomic() so will have to either: > - do the access_ok() verification inside the function
I think open coding the access_ok() check is probably the best option. cheers
