Re: [PATCH 16/36] tty/vt: consolemap: check put_user() in con_get_unimap()

[Jiri Slaby]

On 07. 06. 22, 16:19, Ilpo Järvinen wrote:
> On Tue, 7 Jun 2022, Jiri Slaby wrote:
>
> > Only the return value of copy_to_user() is checked in con_get_unimap().
> > Do the same for put_user() of the count too.
> >
> > Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
> > ---
> >   drivers/tty/vt/consolemap.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
> > index 831450f2bfd1..92b5dddb00d9 100644
> > --- a/drivers/tty/vt/consolemap.c
> > +++ b/drivers/tty/vt/consolemap.c
> > @@ -813,7 +813,8 @@ int con_get_unimap(struct vc_data *vc, ushort ct, ushort __user *uct,
> >   	console_unlock();
> >   	if (copy_to_user(list, unilist, min(ect, ct) * sizeof(*unilist)))
> >   		ret = -EFAULT;
> > -	put_user(ect, uct);
> > +	if (put_user(ect, uct))
> > +		ret = -EFAULT;
> >   	kvfree(unilist);
> >   	return ret ? ret : (ect <= ct) ? 0 : -ENOMEM;
> >   }
>
> Doesn't this fix something?

If you mean a Fixes tag, this is pre-git.

If you mean a bug, well, likely yes, users now get informed. But I don't 
think anyone cares ;). But who knows, maybe we will start seeing 
userspace failures now (as they might not provide writable count field 
-- unlikely). That's one of the reasons why I did this as a separate 
commit. Let's see if are going to revert this or not...

thanks,
--
js
suse labs