vt.c: unimap changes to (fg_?)console

vt.c: unimap changes to (fg_?)console

[Kurt Garloff]

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Hi Linus, Alan, Andries,

if you open /dev/tty4 and change the font via ioctl(KDFONTOP), it will be
applied to the opened console, i.e. tty4. Then you set the corresponding
unicodemap via PIO_UNIMAPCLR and PIO_UNIMAP ioctls. Those get applied to the
current foreground console. Which is inconsistent.

Looking at vt.c: vt_ioctl(), the situation is a bit messy: Some ioctls don't
explicitly specify a tty (probably not needed, as some settings are global),
some apply to fg_console, some apply to the opened console which is
((struct vt_struct*)tty->driver_data)->vc_num.

I would appreciate, if somebody with more knowledge could have a look and
check whether this is all correct. At least for the above case, it's not.
(Andries, I would appreciate if you have a look; you understand much more of
it than I do.)

I attach a patch to fix the specific problem reported above. It applies to
both 2.4.4 and 2.2.19. ioctl(PIO_UNIMAP[CLR]) is applied to the opened
console now instead of fg_console.
Please apply until somebody comes with a complete vt.c cleanup!

If you want to test yourself: I also have a patch against kbd-1.05
which allows you to use setfont -c /dev/ttyXX to specify which terminal you
want to. I already sent it to Andries.

Regards,
-- 
Kurt Garloff  <garloff@suse.de>                          Eindhoven, NL
GPG key: See mail header, key servers         Linux kernel development
SuSE GmbH, Nuernberg, FRG                               SCSI, Security

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--- linux-244.compile/drivers/char/vt.c.orig	Fri Feb  9 20:30:22 2001
+++ linux-244.compile/drivers/char/vt.c	Mon May  7 10:37:25 2001
@@ -392,7 +392,7 @@
 }
 
 static inline int 
-do_unimap_ioctl(int cmd, struct unimapdesc *user_ud,int perm)
+do_unimap_ioctl(int cmd, struct unimapdesc *user_ud, int perm, unsigned int console)
 {
 	struct unimapdesc tmp;
 	int i = 0; 
@@ -408,9 +408,11 @@
 	case PIO_UNIMAP:
 		if (!perm)
 			return -EPERM;
-		return con_set_unimap(fg_console, tmp.entry_ct, tmp.entries);
+		return con_set_unimap(console, tmp.entry_ct, tmp.entries);
 	case GIO_UNIMAP:
-		return con_get_unimap(fg_console, tmp.entry_ct, &(user_ud->entry_ct), tmp.entries);
+		if (!perm && fg_console != console)
+			return -EPERM;
+		return con_get_unimap(console, tmp.entry_ct, &(user_ud->entry_ct), tmp.entries);
 	}
 	return 0;
 }
@@ -1029,13 +1031,13 @@
 			return -EPERM;
 		i = copy_from_user(&ui, (void *)arg, sizeof(struct unimapinit));
 		if (i) return -EFAULT;
-		con_clear_unimap(fg_console, &ui);
+		con_clear_unimap(console, &ui);
 		return 0;
 	      }
 
 	case PIO_UNIMAP:
 	case GIO_UNIMAP:
-		return do_unimap_ioctl(cmd, (struct unimapdesc *)arg, perm);
+		return do_unimap_ioctl(cmd, (struct unimapdesc *)arg, perm, console);
 
 	case VT_LOCKSWITCH:
 		if (!suser())

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Re: vt.c: unimap changes to (fg_?)console

[H. Peter Anvin]

Followup to:  <20010507123709.D8052@garloff.suse.de>
By author:    Kurt Garloff <garloff@suse.de>
In newsgroup: linux.dev.kernel
> 
> Hi Linus, Alan, Andries,
> 
> if you open /dev/tty4 and change the font via ioctl(KDFONTOP), it will be
> applied to the opened console, i.e. tty4. Then you set the corresponding
> unicodemap via PIO_UNIMAPCLR and PIO_UNIMAP ioctls. Those get applied to the
> current foreground console. Which is inconsistent.
> 
> Looking at vt.c: vt_ioctl(), the situation is a bit messy: Some ioctls don't
> explicitly specify a tty (probably not needed, as some settings are global),
> some apply to fg_console, some apply to the opened console which is
> ((struct vt_struct*)tty->driver_data)->vc_num.
> 

Okay, these should either be global or apply to the invoked (file
descriptor) tty.  Anything else is completely broken.  In fact, I'd
argue that using ioctl's for anything but global data (since it's
global, it has to be privileged) is in itself broken.  (Note: all the
font stuff used to be global state for kernel memory reasons.)

Why do you have the following in your patch?  It makes the permissions
on the console depend on whether or not it is in the foreground, which
seems like another stupid inconsistency:

> +		if (!perm && fg_console !=3D console)
> +			return -EPERM;
	-hpa
-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt