linux-kernel - Re: [RFC v1] copy_{to,from}_user(): only inline when !__CHECKER_

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Message-ID: <20181209220839.sf5t3mis4pawqthc@ltop.local>
Date:   Sun, 9 Dec 2018 23:08:40 +0100
From:   Luc Van Oostenryck <luc.vanoostenryck@...il.com>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Tycho Andersen <tycho@...ho.ws>, linux-sparse@...r.kernel.org,
        kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC v1] copy_{to,from}_user(): only inline when !__CHECKER__

On Sun, Dec 09, 2018 at 09:56:51PM +0000, Al Viro wrote:
> On Sun, Dec 09, 2018 at 10:39:52PM +0100, Luc Van Oostenryck wrote:
> 
> > There are several more or less bad/good solutions, like:
> > * add raw_copy_{to,from}_user() in the list of checked function
> >   (not inlined in most archs).
> > * add a new annotation to force sparse to check the byte count
> >   (I'm thinking about __range__/OP_RANGE or something similar).
> > * do these checks before functions are inlined (but then some
> >   constant count could not yet be seen as constant).
>   * just spell it out in copy_to_user() itself - as in
> #ifdef C_T_U_SIZE_LIMIT
> 	if (__builtin_constant_p(count) && count > C_T_U_SIZE_LIMIT)
> 		/* something warning-triggering */
> #endif
> in the beginning of copy_from_user().  Or simply
> #ifdef C_T_U_SIZE_LIMIT
> 	BUILD_BUG_ON(__builtin_constant_p(count) && count > C_T_U_SIZE_LIMIT);
> #endif
> in there...

Yes, I agree.

-- Luc