linux-kernel - Re: [PATCH] Fix KDFONTOP 32bit compatibility layer

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Date:	Tue, 31 Jan 2012 16:35:36 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Samuel Thibault <samuel.thibault@...-lyon.org>
Cc:	linux-kernel@...r.kernel.org,
	"Greg Kroah-Hartman" <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arthur Taylor <art@...ed.ca>, Jiri Slaby <jslaby@...e.cz>,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH] Fix KDFONTOP 32bit compatibility layer

On Saturday 28 January 2012, Samuel Thibault wrote:
> KDFONTOP(GET) currently fails with EIO when being run in a 32bit
> userland with a 64bit kernel if the font width is not 8. This is because
> the compatibility layer introduced by e9216651 forces the addition of
> the KD_FONT_FLAG_OLD flag, which makes con_font_get return EIO in such
> case.  This flag should not be set for KDFONTOP, since it's actually
> the whole point of this flag (see comment in con_font_set for instance).
> 
> Signed-off-by: Samuel Thibault <samuel.thibault@...-lyon.org>

Hmm, this flag was not introduced in the patch you cite, it used to
live in fs/compat_ioctl.c before that, since before the start of the
git history. It seems to date back on the original sparc64 implementation
of do_kdfontop_ioctl that was written by Eddie Dost in 1998.

> diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
> index 5e096f4..65447c5 100644
> --- a/drivers/tty/vt/vt_ioctl.c
> +++ b/drivers/tty/vt/vt_ioctl.c
> @@ -1463,7 +1463,6 @@ compat_kdfontop_ioctl(struct compat_console_font_op __user *fontop,
>         if (!perm && op->op != KD_FONT_OP_GET)
>                 return -EPERM;
>         op->data = compat_ptr(((struct compat_console_font_op *)op)->data);
> -       op->flags |= KD_FONT_FLAG_OLD;
>         i = con_font_op(vc, op);
>         if (i)
>                 return i;

>From all I can tell, the patch looks correct, but please update the
description so you don't blame my innocent patch ;-)

Reviewed-by: Arnd Bergmann <arnd@...db.de>
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