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Date:   Mon, 2 Oct 2023 07:38:42 +0200 (CEST)
From:   Julia Lawall <julia.lawall@inria.fr>
To:     Kees Cook <keescook@chromium.org>
cc:     Julia Lawall <julia.lawall@inria.fr>, Kees Cook <kees@kernel.org>,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        Ian Abbott <abbotti@mev.co.uk>,
        H Hartley Sweeten <hsweeten@visionengravers.com>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>, linux-kernel@vger.kernel.org,
        kernel-janitors@vger.kernel.org, linux-hardening@vger.kernel.org,
        llvm@lists.linux.dev
Subject: Re: [PATCH] comedi: Annotate struct comedi_lrange with
 __counted_by
In-Reply-To: <202310011515.D4C9184@keescook>
Message-ID: <alpine.DEB.2.22.394.2310020737570.3166@hadrien>
References: <5c3b7459b820e22e2ac6ce892d4aadcc119cc919.1696065263.git.christophe.jaillet@wanadoo.fr> <202309301342.5B5BED40A1@keescook> <alpine.DEB.2.22.394.2310010945130.3166@hadrien> <90E2BBA5-8A2D-42DE-B36A-CD37BABBB433@kernel.org>
 <alpine.DEB.2.22.394.2310012112560.3166@hadrien> <202310011405.7599BA9@keescook> <202310011421.C4F19D45@keescook> <202310011515.D4C9184@keescook>
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On Sun, 1 Oct 2023, Kees Cook wrote:

> On Sun, Oct 01, 2023 at 02:22:17PM -0700, Kees Cook wrote:
> > On Sun, Oct 01, 2023 at 02:05:46PM -0700, Kees Cook wrote:
> > > On Sun, Oct 01, 2023 at 09:14:02PM +0200, Julia Lawall wrote:
> > > > Kees,
> > > >
> > > > You can try the following.
> > >
> > > Cool! Yeah, this finds the example:
> > >
> > > drivers/comedi/drivers/rti800.c:74: struct comedi_lrange: field at offset 0 is the counter for the flex array
> > > drivers/comedi/drivers/rti800.c:83: struct comedi_lrange: field at offset 0 is the counter for the flex array
> > > drivers/comedi/drivers/rti800.c:92: struct comedi_lrange: field at offset 0 is the counter for the flex array
> > >
> > > I'll run it on the whole codebase...
> >
> > It found only the struct comedi_lrange instances, but that's good to
> > know. :)
>
> On a related note, why doesn't this work?
>
> @allocated@
> identifier STRUCT, ARRAY;
> expression COUNT;
> struct STRUCT *PTR;
> identifier ALLOC;
> type ELEMENT_TYPE;
> @@
>
>         PTR = ALLOC(..., sizeof(\(*PTR\|struct STRUCT\)) +
>                          COUNT * sizeof(\(*PTR->ARRAY\|PTR->ARRAY[0]\|ELEMENT_TYPE\)), ...);
>
>
> minus: parse error:
>   File "alloc.cocci", line 15, column 34, charpos = 485
>   around = 'struct',
>   whole content =       PTR = ALLOC(..., sizeof(\(*PTR\|struct STRUCT\)) +
>
> if I drop "struct", then it complains about ELEMENT_TYPE...

The sizeof with an expression argument is treated differently than the
sizeof with a type argument.  So you need to write:

@allocated@
identifier STRUCT, ARRAY;
expression COUNT;
struct STRUCT *PTR;
identifier ALLOC;
type ELEMENT_TYPE;
@@

        PTR = ALLOC(..., \(sizeof(*PTR)\|sizeof(struct STRUCT)\) +
                         COUNT * \(sizeof(*PTR->ARRAY)\|sizeof(PTR->ARRAY[0])\|sizeof(ELEMENT_TYPE)\), ...);

julia