Re: [PATCH] tty: vt: keyboard: do not copy an extra-byte in copy_to_user

Ajay Garg
2021-11-06T20:44:52Z

> >
> > That's the whole point of the discussion :)
> >
> > The method "vt_do_kdgkb_ioctl" does not manage "func_table[kb_func]".
> > Thus, the method does not know whether or not
> > strlen(func_table[kb_func]) < sizeof(user_kdgkb->kb_string).
> >
>
> It manages. The code under `case KDSKBSENT:` sets func_table[] entries
> via vt_kdskbsent().
>
> kbs = strndup_user(..., sizeof(user_kdgkb->kb_string));
>
> is used to allocate buffer for the func_table[] entry. That's my main
> point :)

func_table is set in vt_kdskbent, which itself is external.

More importantly, vt_kdskbent is handled in case KDSKBSENT:, while the
strlcpy issue we are dealing with is in case KDGKBSENT:
In case KDGKBSENT, following are managed :

ssize_t len = sizeof(user_kdgkb->kb_string);
kbs = kmalloc(len, GFP_KERNEL);

while func_table[kb_func] is external entity here, so no assumption
ought to be made for it, just my 2 cents though :)

Anyhow, really, it is the maintainers' choice now :), since there
isn't a burning (compilation/runtime) issue.

>
>
>
>
> With regards,
> Pavel Skripkin