Re: [PATCH v2 1/2] vt: vt_ioctl: fix VT_DISALLOCATE freeing in-use virtual console

Greg Kroah-Hartman
2020-03-20T06:58:03Z

On Thu, Mar 19, 2020 at 10:10:49PM -0700, Eric Biggers wrote:
> On Thu, Mar 19, 2020 at 08:36:28AM +0100, Jiri Slaby wrote:
> > On 18. 03. 20, 23:38, Eric Biggers wrote:
> > > --- a/drivers/tty/vt/vt.c
> > > +++ b/drivers/tty/vt/vt.c
> > > @@ -1102,6 +1102,9 @@ int vc_allocate(unsigned int currcons) /* return 0 on success */
> > > tty_port_init(&vc->port);
> > > INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
> > >
> > > + /* if this wasn't the case, we'd have to implement port->ops.destruct */
> > > + BUILD_BUG_ON(offsetof(struct vc_data, port) != 0);
> > > +
> >
> > This is 3 lines, implementing destruct would be like 4-5 :)? Please
> > implement destruct instead.
> >
> > Otherwise looks good.
> >
>
> Actually implementing destruct would be 12 lines, see below. Remember there is
> no tty_port_operations defined yet so we'd have to define it just for destruct.
>
> Do you still prefer it?
>
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index ec34f1f5f3bb5..309a39197be0a 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -1075,6 +1075,17 @@ static void visual_deinit(struct vc_data *vc)
> module_put(vc->vc_sw->owner);
> }
>
> +static void vc_port_destruct(struct tty_port *port)
> +{
> + struct vc_data *vc = container_of(port, struct vc_data, port);
> +
> + kfree(vc);
> +}
> +
> +static const struct tty_port_operations vc_port_ops = {
> + .destruct = vc_port_destruct,
> +};
> +
> int vc_allocate(unsigned int currcons) /* return 0 on success */
> {
> struct vt_notifier_param param;
> @@ -1100,11 +1111,9 @@ int vc_allocate(unsigned int currcons) /* return 0 on success */
>
> vc_cons[currcons].d = vc;
> tty_port_init(&vc->port);
> + vc->port.ops = &vc_port_ops;
> INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
>
> - /* if this wasn't the case, we'd have to implement port->ops.destruct */
> - BUILD_BUG_ON(offsetof(struct vc_data, port) != 0);
> -
> visual_init(vc, currcons, 1);
>
> if (!*vc->vc_uni_pagedir_loc)

Yes, this is good to have, thanks for doing this.

greg k-h