linux-kernel - Re: dm ioctl: Use struct

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Date:   Wed, 17 Jun 2020 12:30:08 -0400
From:   Mike Snitzer <snitzer@...hat.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Alasdair Kergon <agk@...hat.com>, dm-devel@...hat.com,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: Re: dm ioctl: Use struct_size() helper

On Tue, Jun 16 2020 at  6:06pm -0400,
Gustavo A. R. Silva <gustavo@...eddedor.com> wrote:

> Hi all,
> 
> Friendly ping: who can take this?
> 
> It's been almost a year... and I just noticed there was a problem
> with the email addresses back then...
> 
> I just fixed the issue and this patch should now appear on
> dm-devel@...hat.com and LKML.

I don't see any resubmit from you on either list.  But I've applied the
fix by hand and attributed it to you.

Thanks,
Mike


> On 8/28/19 13:38, Gustavo A. R. Silva wrote:
> > One of the more common cases of allocation size calculations is finding
> > the size of a structure that has a zero-sized array at the end, along
> > with memory for some number of elements for that array. For example:
> > 
> > struct dm_target_deps {
> > 	...
> >         __u64 dev[0];   /* out */
> > };
> > 
> > Make use of the struct_size() helper instead of an open-coded version
> > in order to avoid any potential type mistakes.
> > 
> > So, replace the following form:
> > 
> > sizeof(*deps) + (sizeof(*deps->dev) * count)
> > 
> > with:
> > 
> > struct_size(deps, dev, count)
> > 
> > This code was detected with the help of Coccinelle.
> > 
> > Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> > ---
> >  drivers/md/dm-ioctl.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> > index fb6f8fb1f13d..b2d52cec70d4 100644
> > --- a/drivers/md/dm-ioctl.c
> > +++ b/drivers/md/dm-ioctl.c
> > @@ -1446,7 +1446,7 @@ static void retrieve_deps(struct dm_table *table,
> >  	/*
> >  	 * Check we have enough space.
> >  	 */
> > -	needed = sizeof(*deps) + (sizeof(*deps->dev) * count);
> > +	needed = struct_size(deps, dev, count);
> >  	if (len < needed) {
> >  		param->flags |= DM_BUFFER_FULL_FLAG;
> >  		return;
> > 
>