linux-kernel - Re: [PATCH] drivers/tty/vt: copy userspace arrays safely

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Date:   Fri, 3 Nov 2023 06:24:09 +1000
From:   David Airlie <airlied@...hat.com>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Philipp Stanner <pstanner@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Tony Luck <tony.luck@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH] drivers/tty/vt: copy userspace arrays safely

On Fri, Nov 3, 2023 at 6:14 AM Al Viro <viro@...iv.linux.org.uk> wrote:
>
> On Thu, Nov 02, 2023 at 08:21:35PM +0100, Philipp Stanner wrote:
> > The functions (v)memdup_user() are utilized to copy userspace arrays.
> > This is done without overflow checks.
> >
> > Use the new wrappers memdup_array_user() and vmemdup_array_user() to
> > copy the arrays more safely.
>
> > @@ -644,7 +644,7 @@ int con_set_unimap(struct vc_data *vc, ushort ct, struct unipair __user *list)
> >       if (!ct)
> >               return 0;
>
> > -     unilist = vmemdup_user(list, array_size(sizeof(*unilist), ct));
> > +     unilist = vmemdup_array_user(list, ct, sizeof(*unilist));
> >       if (IS_ERR(unilist))
> >               return PTR_ERR(unilist);
>
> a 16bit value times sizeof(something).

So since it's already using array_size here, moving it to a new helper
for consistency just makes things clearer, and so you are fine with
the patch?

Otherwise I'd think you are been a snarky asshole to a coworker.

Dave.