Commit message: vt: vt_ioctl: fix race in VT_RESIZEX

We need to make sure vc_cons[i].d is not NULL after grabbing
console_lock(), or risk a crash.

general protection fault, probably for non-canonical address 0xdffffc0000000068: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000340-0x0000000000000347]
CPU: 1 PID: 19462 Comm: syz-executor.5 Not tainted 5.5.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:vt_ioctl+0x1f96/0x26d0 drivers/tty/vt/vt_ioctl.c:883
Code: 74 41 e8 bd a6 84 fd 48 89 d8 48 c1 e8 03 42 80 3c 28 00 0f 85 e4 04 00 00 48 8b 03 48 8d b8 40 03 00 00 48 89 fa 48 c1 ea 03 <42> 0f b6 14 2a 84 d2 74 09 80 fa 03 0f 8e b1 05 00 00 44 89 b8 40
RSP: 0018:ffffc900086d7bb0 EFLAGS: 00010202
RAX: 0000000000000000 RBX: ffffffff8c34ee88 RCX: ffffc9001415c000
RDX: 0000000000000068 RSI: ffffffff83f0e6e3 RDI: 0000000000000340
RBP: ffffc900086d7cd0 R08: ffff888054ce0100 R09: fffffbfff16a2f6d
R10: ffff888054ce0998 R11: ffff888054ce0100 R12: 000000000000001d
R13: dffffc0000000000 R14: 1ffff920010daf79 R15: 000000000000ff7f
FS:  00007f7d13c12700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd477e3c38 CR3: 0000000095d0a000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2660
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45b399
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f7d13c11c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f7d13c126d4 RCX: 000000000045b399
RDX: 0000000020000080 RSI: 000000000000560a RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000666 R14: 00000000004c7f04 R15: 000000000075bf2c
Modules linked in:
---[ end trace 80970faf7a67eb77 ]---
RIP: 0010:vt_ioctl+0x1f96/0x26d0 drivers/tty/vt/vt_ioctl.c:883
Code: 74 41 e8 bd a6 84 fd 48 89 d8 48 c1 e8 03 42 80 3c 28 00 0f 85 e4 04 00 00 48 8b 03 48 8d b8 40 03 00 00 48 89 fa 48 c1 ea 03 <42> 0f b6 14 2a 84 d2 74 09 80 fa 03 0f 8e b1 05 00 00 44 89 b8 40
RSP: 0018:ffffc900086d7bb0 EFLAGS: 00010202
RAX: 0000000000000000 RBX: ffffffff8c34ee88 RCX: ffffc9001415c000
RDX: 0000000000000068 RSI: ffffffff83f0e6e3 RDI: 0000000000000340
RBP: ffffc900086d7cd0 R08: ffff888054ce0100 R09: fffffbfff16a2f6d
R10: ffff888054ce0998 R11: ffff888054ce0100 R12: 000000000000001d
R13: dffffc0000000000 R14: 1ffff920010daf79 R15: 000000000000ff7f
FS:  00007f7d13c12700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd477e3c38 CR3: 0000000095d0a000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: stable <stable@vger.kernel.org>
Reported-by: syzbot <syzkaller@googlegroups.com>
Link: https://lore.kernel.org/r/20200210190721.200418-1-edumazet@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CVE: CVE-2020-36558
CWE: CWE-703
Vulnerability description: A race condition in the Linux kernel before 5.5.7 involving VT_RESIZEX could lead to a NULL pointer dereference and general protection fault.

Project: linux
File: vt_ioctl.c

int vt_ioctl(struct tty_struct *tty,
	     unsigned int cmd, unsigned long arg)
{
	struct vc_data *vc = tty->driver_data;
	struct console_font_op op;	/* used in multiple places here */
	unsigned int console;
	unsigned char ucval;
	unsigned int uival;
	void __user *up = (void __user *)arg;
	int i, perm;
	int ret = 0;

	console = vc->vc_num;


	if (!vc_cons_allocated(console)) { 	/* impossible? */
		ret = -ENOIOCTLCMD;
		goto out;
	}


	/*
	 * To have permissions to do most of the vt ioctls, we either have
	 * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
	 */
	perm = 0;
	if (current->signal->tty == tty || capable(CAP_SYS_TTY_CONFIG))
		perm = 1;
 
	switch (cmd) {
	case TIOCLINUX:
		ret = tioclinux(tty, arg);
		break;
	case KIOCSOUND:
		if (!perm)
			return -EPERM;
		/*
		 * The use of PIT_TICK_RATE is historic, it used to be
		 * the platform-dependent CLOCK_TICK_RATE between 2.6.12
		 * and 2.6.36, which was a minor but unfortunate ABI
		 * change. kd_mksound is locked by the input layer.
		 */
		if (arg)
			arg = PIT_TICK_RATE / arg;
		kd_mksound(arg, 0);
		break;

	case KDMKTONE:
		if (!perm)
			return -EPERM;
	{
		unsigned int ticks, count;
		
		/*
		 * Generate the tone for the appropriate number of ticks.
		 * If the time is zero, turn off sound ourselves.
		 */
		ticks = msecs_to_jiffies((arg >> 16) & 0xffff);
		count = ticks ? (arg & 0xffff) : 0;
		if (count)
			count = PIT_TICK_RATE / count;
		kd_mksound(count, ticks);
		break;
	}

	case KDGKBTYPE:
		/*
		 * this is naïve.
		 */
		ucval = KB_101;
		ret = put_user(ucval, (char __user *)arg);
		break;

		/*
		 * These cannot be implemented on any machine that implements
		 * ioperm() in user level (such as Alpha PCs) or not at all.
		 *
		 * XXX: you should never use these, just call ioperm directly..
		 */
#ifdef CONFIG_X86
	case KDADDIO:
	case KDDELIO:
		/*
		 * KDADDIO and KDDELIO may be able to add ports beyond what
		 * we reject here, but to be safe...
		 *
		 * These are locked internally via sys_ioperm
		 */
		if (arg < GPFIRST || arg > GPLAST) {
			ret = -EINVAL;
			break;
		}
		ret = ksys_ioperm(arg, 1, (cmd == KDADDIO)) ? -ENXIO : 0;
		break;

	case KDENABIO:
	case KDDISABIO:
		ret = ksys_ioperm(GPFIRST, GPNUM,
				  (cmd == KDENABIO)) ? -ENXIO : 0;
		break;
#endif

	/* Linux m68k/i386 interface for setting the keyboard delay/repeat rate */
		
	case KDKBDREP:
	{
		struct kbd_repeat kbrep;
		
		if (!capable(CAP_SYS_TTY_CONFIG))
			return -EPERM;

		if (copy_from_user(&kbrep, up, sizeof(struct kbd_repeat))) {
			ret =  -EFAULT;
			break;
		}
		ret = kbd_rate(&kbrep);
		if (ret)
			break;
		if (copy_to_user(up, &kbrep, sizeof(struct kbd_repeat)))
			ret = -EFAULT;
		break;
	}

	case KDSETMODE:
		/*
		 * currently, setting the mode from KD_TEXT to KD_GRAPHICS
		 * doesn't do a whole lot. i'm not sure if it should do any
		 * restoration of modes or what...
		 *
		 * XXX It should at least call into the driver, fbdev's definitely
		 * need to restore their engine state. --BenH
		 */
		if (!perm)
			return -EPERM;
		switch (arg) {
		case KD_GRAPHICS:
			break;
		case KD_TEXT0:
		case KD_TEXT1:
			arg = KD_TEXT;
		case KD_TEXT:
			break;
		default:
			ret = -EINVAL;
			goto out;
		}
		/* FIXME: this needs the console lock extending */
		if (vc->vc_mode == (unsigned char) arg)
			break;
		vc->vc_mode = (unsigned char) arg;
		if (console != fg_console)
			break;
		/*
		 * explicitly blank/unblank the screen if switching modes
		 */
		console_lock();
		if (arg == KD_TEXT)
			do_unblank_screen(1);
		else
			do_blank_screen(1);
		console_unlock();
		break;

	case KDGETMODE:
		uival = vc->vc_mode;
		goto setint;

	case KDMAPDISP:
	case KDUNMAPDISP:
		/*
		 * these work like a combination of mmap and KDENABIO.
		 * this could be easily finished.
		 */
		ret = -EINVAL;
		break;

	case KDSKBMODE:
		if (!perm)
			return -EPERM;
		ret = vt_do_kdskbmode(console, arg);
		if (ret == 0)
			tty_ldisc_flush(tty);
		break;

	case KDGKBMODE:
		uival = vt_do_kdgkbmode(console);
		ret = put_user(uival, (int __user *)arg);
		break;

	/* this could be folded into KDSKBMODE, but for compatibility
	   reasons it is not so easy to fold KDGKBMETA into KDGKBMODE */
	case KDSKBMETA:
		ret = vt_do_kdskbmeta(console, arg);
		break;

	case KDGKBMETA:
		/* FIXME: should review whether this is worth locking */
		uival = vt_do_kdgkbmeta(console);
	setint:
		ret = put_user(uival, (int __user *)arg);
		break;

	case KDGETKEYCODE:
	case KDSETKEYCODE:
		if(!capable(CAP_SYS_TTY_CONFIG))
			perm = 0;
		ret = vt_do_kbkeycode_ioctl(cmd, up, perm);
		break;

	case KDGKBENT:
	case KDSKBENT:
		ret = vt_do_kdsk_ioctl(cmd, up, perm, console);
		break;

	case KDGKBSENT:
	case KDSKBSENT:
		ret = vt_do_kdgkb_ioctl(cmd, up, perm);
		break;

	/* Diacritical processing. Handled in keyboard.c as it has
	   to operate on the keyboard locks and structures */
	case KDGKBDIACR:
	case KDGKBDIACRUC:
	case KDSKBDIACR:
	case KDSKBDIACRUC:
		ret = vt_do_diacrit(cmd, up, perm);
		break;

	/* the ioctls below read/set the flags usually shown in the leds */
	/* don't use them - they will go away without warning */
	case KDGKBLED:
	case KDSKBLED:
	case KDGETLED:
	case KDSETLED:
		ret = vt_do_kdskled(console, cmd, arg, perm);
		break;

	/*
	 * A process can indicate its willingness to accept signals
	 * generated by pressing an appropriate key combination.
	 * Thus, one can have a daemon that e.g. spawns a new console
	 * upon a keypress and then changes to it.
	 * See also the kbrequest field of inittab(5).
	 */
	case KDSIGACCEPT:
	{
		if (!perm || !capable(CAP_KILL))
			return -EPERM;
		if (!valid_signal(arg) || arg < 1 || arg == SIGKILL)
			ret = -EINVAL;
		else {
			spin_lock_irq(&vt_spawn_con.lock);
			put_pid(vt_spawn_con.pid);
			vt_spawn_con.pid = get_pid(task_pid(current));
			vt_spawn_con.sig = arg;
			spin_unlock_irq(&vt_spawn_con.lock);
		}
		break;
	}

	case VT_SETMODE:
	{
		struct vt_mode tmp;

		if (!perm)
			return -EPERM;
		if (copy_from_user(&tmp, up, sizeof(struct vt_mode))) {
			ret = -EFAULT;
			goto out;
		}
		if (tmp.mode != VT_AUTO && tmp.mode != VT_PROCESS) {
			ret = -EINVAL;
			goto out;
		}
		console_lock();
		vc->vt_mode = tmp;
		/* the frsig is ignored, so we set it to 0 */
		vc->vt_mode.frsig = 0;
		put_pid(vc->vt_pid);
		vc->vt_pid = get_pid(task_pid(current));
		/* no switch is required -- saw@shade.msu.ru */
		vc->vt_newvt = -1;
		console_unlock();
		break;
	}

	case VT_GETMODE:
	{
		struct vt_mode tmp;
		int rc;

		console_lock();
		memcpy(&tmp, &vc->vt_mode, sizeof(struct vt_mode));
		console_unlock();

		rc = copy_to_user(up, &tmp, sizeof(struct vt_mode));
		if (rc)
			ret = -EFAULT;
		break;
	}

	/*
	 * Returns global vt state. Note that VT 0 is always open, since
	 * it's an alias for the current VT, and people can't use it here.
	 * We cannot return state for more than 16 VTs, since v_state is short.
	 */
	case VT_GETSTATE:
	{
		struct vt_stat __user *vtstat = up;
		unsigned short state, mask;

		/* Review: FIXME: Console lock ? */
		if (put_user(fg_console + 1, &vtstat->v_active))
			ret = -EFAULT;
		else {
			state = 1;	/* /dev/tty0 is always open */
			for (i = 0, mask = 2; i < MAX_NR_CONSOLES && mask;
							++i, mask <<= 1)
				if (VT_IS_IN_USE(i))
					state |= mask;
			ret = put_user(state, &vtstat->v_state);
		}
		break;
	}

	/*
	 * Returns the first available (non-opened) console.
	 */
	case VT_OPENQRY:
		/* FIXME: locking ? - but then this is a stupid API */
		for (i = 0; i < MAX_NR_CONSOLES; ++i)
			if (! VT_IS_IN_USE(i))
				break;
		uival = i < MAX_NR_CONSOLES ? (i+1) : -1;
		goto setint;		 

	/*
	 * ioctl(fd, VT_ACTIVATE, num) will cause us to switch to vt # num,
	 * with num >= 1 (switches to vt 0, our console, are not allowed, just
	 * to preserve sanity).
	 */
	case VT_ACTIVATE:
		if (!perm)
			return -EPERM;
		if (arg == 0 || arg > MAX_NR_CONSOLES)
			ret =  -ENXIO;
		else {
			arg--;
			console_lock();
			ret = vc_allocate(arg);
			console_unlock();
			if (ret)
				break;
			set_console(arg);
		}
		break;

	case VT_SETACTIVATE:
	{
		struct vt_setactivate vsa;

		if (!perm)
			return -EPERM;

		if (copy_from_user(&vsa, (struct vt_setactivate __user *)arg,
					sizeof(struct vt_setactivate))) {
			ret = -EFAULT;
			goto out;
		}
		if (vsa.console == 0 || vsa.console > MAX_NR_CONSOLES)
			ret = -ENXIO;
		else {
			vsa.console = array_index_nospec(vsa.console,
							 MAX_NR_CONSOLES + 1);
			vsa.console--;
			console_lock();
			ret = vc_allocate(vsa.console);
			if (ret == 0) {
				struct vc_data *nvc;
				/* This is safe providing we don't drop the
				   console sem between vc_allocate and
				   finishing referencing nvc */
				nvc = vc_cons[vsa.console].d;
				nvc->vt_mode = vsa.mode;
				nvc->vt_mode.frsig = 0;
				put_pid(nvc->vt_pid);
				nvc->vt_pid = get_pid(task_pid(current));
			}
			console_unlock();
			if (ret)
				break;
			/* Commence switch and lock */
			/* Review set_console locks */
			set_console(vsa.console);
		}
		break;
	}

	/*
	 * wait until the specified VT has been activated
	 */
	case VT_WAITACTIVE:
		if (!perm)
			return -EPERM;
		if (arg == 0 || arg > MAX_NR_CONSOLES)
			ret = -ENXIO;
		else
			ret = vt_waitactive(arg);
		break;

	/*
	 * If a vt is under process control, the kernel will not switch to it
	 * immediately, but postpone the operation until the process calls this
	 * ioctl, allowing the switch to complete.
	 *
	 * According to the X sources this is the behavior:
	 *	0:	pending switch-from not OK
	 *	1:	pending switch-from OK
	 *	2:	completed switch-to OK
	 */
	case VT_RELDISP:
		if (!perm)
			return -EPERM;

		console_lock();
		if (vc->vt_mode.mode != VT_PROCESS) {
			console_unlock();
			ret = -EINVAL;
			break;
		}
		/*
		 * Switching-from response
		 */
		if (vc->vt_newvt >= 0) {
			if (arg == 0)
				/*
				 * Switch disallowed, so forget we were trying
				 * to do it.
				 */
				vc->vt_newvt = -1;

			else {
				/*
				 * The current vt has been released, so
				 * complete the switch.
				 */
				int newvt;
				newvt = vc->vt_newvt;
				vc->vt_newvt = -1;
				ret = vc_allocate(newvt);
				if (ret) {
					console_unlock();
					break;
				}
				/*
				 * When we actually do the console switch,
				 * make sure we are atomic with respect to
				 * other console switches..
				 */
				complete_change_console(vc_cons[newvt].d);
			}
		} else {
			/*
			 * Switched-to response
			 */
			/*
			 * If it's just an ACK, ignore it
			 */
			if (arg != VT_ACKACQ)
				ret = -EINVAL;
		}
		console_unlock();
		break;

	 /*
	  * Disallocate memory associated to VT (but leave VT1)
	  */
	 case VT_DISALLOCATE:
		if (arg > MAX_NR_CONSOLES) {
			ret = -ENXIO;
			break;
		}
		if (arg == 0)
			vt_disallocate_all();
		else
			ret = vt_disallocate(--arg);
		break;

	case VT_RESIZE:
	{
		struct vt_sizes __user *vtsizes = up;
		struct vc_data *vc;

		ushort ll,cc;
		if (!perm)
			return -EPERM;
		if (get_user(ll, &vtsizes->v_rows) ||
		    get_user(cc, &vtsizes->v_cols))
			ret = -EFAULT;
		else {
			console_lock();
			for (i = 0; i < MAX_NR_CONSOLES; i++) {
				vc = vc_cons[i].d;

				if (vc) {
					vc->vc_resize_user = 1;
					/* FIXME: review v tty lock */
					vc_resize(vc_cons[i].d, cc, ll);
				}
			}
			console_unlock();
		}
		break;
	}

	case VT_RESIZEX:
	{
		struct vt_consize v;
		if (!perm)
			return -EPERM;
		if (copy_from_user(&v, up, sizeof(struct vt_consize)))
			return -EFAULT;
		/* FIXME: Should check the copies properly */
		if (!v.v_vlin)
			v.v_vlin = vc->vc_scan_lines;
		if (v.v_clin) {
			int rows = v.v_vlin/v.v_clin;
			if (v.v_rows != rows) {
				if (v.v_rows) /* Parameters don't add up */
					return -EINVAL;
				v.v_rows = rows;
			}
		}
		if (v.v_vcol && v.v_ccol) {
			int cols = v.v_vcol/v.v_ccol;
			if (v.v_cols != cols) {
				if (v.v_cols)
					return -EINVAL;
				v.v_cols = cols;
			}
		}

		if (v.v_clin > 32)
			return -EINVAL;

		for (i = 0; i < MAX_NR_CONSOLES; i++) {
			if (!vc_cons[i].d)
				continue;
			console_lock();
			if (v.v_vlin)
				vc_cons[i].d->vc_scan_lines = v.v_vlin;
			if (v.v_clin)
				vc_cons[i].d->vc_font.height = v.v_clin;
			vc_cons[i].d->vc_resize_user = 1;
			vc_resize(vc_cons[i].d, v.v_cols, v.v_rows);
			console_unlock();
		}
		break;
	}

	case PIO_FONT: {
		if (!perm)
			return -EPERM;
		op.op = KD_FONT_OP_SET;
		op.flags = KD_FONT_FLAG_OLD | KD_FONT_FLAG_DONT_RECALC;	/* Compatibility */
		op.width = 8;
		op.height = 0;
		op.charcount = 256;
		op.data = up;
		ret = con_font_op(vc_cons[fg_console].d, &op);
		break;
	}

	case GIO_FONT: {
		op.op = KD_FONT_OP_GET;
		op.flags = KD_FONT_FLAG_OLD;
		op.width = 8;
		op.height = 32;
		op.charcount = 256;
		op.data = up;
		ret = con_font_op(vc_cons[fg_console].d, &op);
		break;
	}

	case PIO_CMAP:
                if (!perm)
			ret = -EPERM;
		else
	                ret = con_set_cmap(up);
		break;

	case GIO_CMAP:
                ret = con_get_cmap(up);
		break;

	case PIO_FONTX:
	case GIO_FONTX:
		ret = do_fontx_ioctl(cmd, up, perm, &op);
		break;

	case PIO_FONTRESET:
	{
		if (!perm)
			return -EPERM;

#ifdef BROKEN_GRAPHICS_PROGRAMS
		/* With BROKEN_GRAPHICS_PROGRAMS defined, the default
		   font is not saved. */
		ret = -ENOSYS;
		break;
#else
		{
		op.op = KD_FONT_OP_SET_DEFAULT;
		op.data = NULL;
		ret = con_font_op(vc_cons[fg_console].d, &op);
		if (ret)
			break;
		console_lock();
		con_set_default_unimap(vc_cons[fg_console].d);
		console_unlock();
		break;
		}
#endif
	}

	case KDFONTOP: {
		if (copy_from_user(&op, up, sizeof(op))) {
			ret = -EFAULT;
			break;
		}
		if (!perm && op.op != KD_FONT_OP_GET)
			return -EPERM;
		ret = con_font_op(vc, &op);
		if (ret)
			break;
		if (copy_to_user(up, &op, sizeof(op)))
			ret = -EFAULT;
		break;
	}

	case PIO_SCRNMAP:
		if (!perm)
			ret = -EPERM;
		else
			ret = con_set_trans_old(up);
		break;

	case GIO_SCRNMAP:
		ret = con_get_trans_old(up);
		break;

	case PIO_UNISCRNMAP:
		if (!perm)
			ret = -EPERM;
		else
			ret = con_set_trans_new(up);
		break;

	case GIO_UNISCRNMAP:
		ret = con_get_trans_new(up);
		break;

	case PIO_UNIMAPCLR:
		if (!perm)
			return -EPERM;
		con_clear_unimap(vc);
		break;

	case PIO_UNIMAP:
	case GIO_UNIMAP:
		ret = do_unimap_ioctl(cmd, up, perm, vc);
		break;

	case VT_LOCKSWITCH:
		if (!capable(CAP_SYS_TTY_CONFIG))
			return -EPERM;
		vt_dont_switch = 1;
		break;
	case VT_UNLOCKSWITCH:
		if (!capable(CAP_SYS_TTY_CONFIG))
			return -EPERM;
		vt_dont_switch = 0;
		break;
	case VT_GETHIFONTMASK:
		ret = put_user(vc->vc_hi_font_mask,
					(unsigned short __user *)arg);
		break;
	case VT_WAITEVENT:
		ret = vt_event_wait_ioctl((struct vt_event __user *)arg);
		break;
	default:
		ret = -ENOIOCTLCMD;
	}
out:
	return ret;
}