Re: dm ioctl: Use struct_size() helper

Mike Snitzer
2020-06-17T16:30:21Z

On Tue, Jun 16 2020 at 6:06pm -0400,
Gustavo A. R. Silva <gustavo@embeddedor.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@redhat.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@embeddedor.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;
> >
>