linux-kernel - Re: [Cocci] [PATCH] coccinelle: misc: add array_size_dup script to detect missed overlow checks

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Date:   Thu, 18 Jun 2020 21:56:18 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Kees Cook <keescook@...omium.org>
cc:     cocci@...teme.lip6.fr, linux-kernel@...r.kernel.org
Subject: Re: [Cocci] [PATCH] coccinelle: misc: add array_size_dup script to
 detect missed overlow checks



On Thu, 18 Jun 2020, Kees Cook wrote:

> On Wed, Jun 17, 2020 at 08:54:03PM +0200, Julia Lawall wrote:
> >
> >
> > On Wed, 17 Jun 2020, Kees Cook wrote:
> >
> > > On Mon, Jun 15, 2020 at 01:20:45PM +0300, Denis Efremov wrote:
> > > > +@as@
> > > > +expression E1, E2;
> > > > +@@
> > > > +
> > > > +array_size(E1, E2)
> > >
> > > BTW, is there a way yet in Coccinelle to match a fully qualified (?)
> > > identifier? For example, if I have two lines in C:
> > >
> > > A)
> > > 	array_size(variable, 5);
> > > B)
> > > 	array_size(instance->member.size, 5);
> > > C)
> > > 	array_size(instance->member.size + 1, 5);
> > > D)
> > > 	array_size(function_call(variable), 5);
> > >
> > >
> > > This matches A, B, C, and D:
> > >
> > > @@
> > > expression ARG1;
> > > expression ARG2;
> > > @@
> > >
> > > array_size(ARG1, ARG2);
> > >
> > >
> > > This matches only A:
> > >
> > > @@
> > > identifier ARG1;
> > > expression ARG2;
> > > @@
> > >
> > > array_size(ARG1, ARG2);
> > >
> > >
> > > How do I get something to match A and B but not C and D (i.e. I do not
> > > want to match any operations, function calls, etc, only a variable,
> > > which may be identified through dereference, array index, or struct
> > > member access.)
> >
> > \(i\|e.fld\|e->fld\)
> >
> > would probably do what you want.  It will also match cases where e is a
> > function/macr call, but that is unlikely.
> >
> > If you want a single metavariable that contains the whole thing, you can
> > have an expression metavariable E and then write:
> >
> > \(\(i\|e.fld\|e->fld\) \& E\)
>
> Can you give an example of how that would look for an @@ section?
>
> The problem I have is that I don't know the depth or combination of such
> metavariables. There are a lot of combinations:
>
> a
> 	a.b
> 		a.b.c
> 			a.b.c.d
> 			a.b.c->d
> 		a.b->c
> 			a.b->c.d
> 			a.b->c->d
> 	a->b
> 		a->b.c
> 			a->b.c.d
> 			a->b.c->d
> 		a->b->c
> 			a->b->c.d
> 			a->b->c->d
> ...


@@
identifier i,fld;
expression e;
@@

\(\(i\|e.fld\|e->fld\) \& E\)

The e will match all of the variants you are concerned about.

julia



>
>
> --
> Kees Cook
>