From 4ef9992ca7dbb6a2617f8daedc142d61ab019ce2 Mon Sep 17 00:00:00 2001
From: hselasky <hselasky@ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f>
Date: Thu, 21 May 2015 07:34:08 +0000
Subject: [PATCH] MFC r282645, r282646 and r282730: * Prevent switching to NULL
 or own window in the "vt_proc_window_switch"   function. This fixes an issue
 where X11 keyboard input can appear   stuck. The cause of the problem is a
 duplicate TTY device window   switch IOCTL during boot, which leaves the
 "vt_switch_timer" running,   because the current window is already selected.
 While at it factor out   some NULL checks. * The "SYSCTL_INT()" default value
 is only used for read only SYSCTLs   and is not applicable unless the integer
 pointer is NULL. Set it to   zero to avoid confusion. While at it remove
 extra semicolon at the end   of the "VT_SYSCTL_INT()" macro. * Ensure the
 result from signed subtraction under modulus does not   become negative.

PR:			200032


git-svn-id: svn://svn.freebsd.org/base/stable/10@283187 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
---
 sys/dev/vt/vt.h      |  6 +++---
 sys/dev/vt/vt_core.c | 42 ++++++++++++++++++++++++++++++------------
 2 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/sys/dev/vt/vt.h b/sys/dev/vt/vt.h
index ab291e6c9..05ae3e241 100644
--- a/sys/dev/vt/vt.h
+++ b/sys/dev/vt/vt.h
@@ -83,10 +83,10 @@
 #define	ISSIGVALID(sig)	((sig) > 0 && (sig) < NSIG)
 
 #define	VT_SYSCTL_INT(_name, _default, _descr)				\
-static int vt_##_name = _default;					\
-SYSCTL_INT(_kern_vt, OID_AUTO, _name, CTLFLAG_RW, &vt_##_name, _default,\
+static int vt_##_name = (_default);					\
+SYSCTL_INT(_kern_vt, OID_AUTO, _name, CTLFLAG_RWTUN, &vt_##_name, 0,	\
 		_descr);						\
-TUNABLE_INT("kern.vt." #_name, &vt_##_name);
+TUNABLE_INT("kern.vt." #_name, &vt_##_name)
 
 struct vt_driver;
 
diff --git a/sys/dev/vt/vt_core.c b/sys/dev/vt/vt_core.c
index 9b723c8df..eee777745 100644
--- a/sys/dev/vt/vt_core.c
+++ b/sys/dev/vt/vt_core.c
@@ -448,12 +448,35 @@ vt_proc_window_switch(struct vt_window *vw)
 	struct vt_device *vd;
 	int ret;
 
+	/* Prevent switching to NULL */
+	if (vw == NULL) {
+		DPRINTF(30, "%s: Cannot switch: vw is NULL.", __func__);
+		return (EINVAL);
+	}
 	vd = vw->vw_device;
 	curvw = vd->vd_curwindow;
 
+	/* Check if virtual terminal is locked */
 	if (curvw->vw_flags & VWF_VTYLOCK)
 		return (EBUSY);
 
+	/* Check if switch already in progress */
+	if (curvw->vw_flags & VWF_SWWAIT_REL) {
+		/* Check if switching to same window */
+		if (curvw->vw_switch_to == vw) {
+			DPRINTF(30, "%s: Switch in progress to same vw.", __func__);
+			return (0);	/* success */
+		}
+		DPRINTF(30, "%s: Switch in progress to different vw.", __func__);
+		return (EBUSY);
+	}
+
+	/* Avoid switching to already selected window */
+	if (vw == curvw) {
+		DPRINTF(30, "%s: Cannot switch: vw == curvw.", __func__);
+		return (0);	/* success */
+	}
+
 	/* Ask current process permission to switch away. */
 	if (curvw->vw_smode.mode == VT_PROCESS) {
 		DPRINTF(30, "%s: VT_PROCESS ", __func__);
@@ -661,8 +684,7 @@ vt_scrollmode_kbdevent(struct vt_window *vw, int c, int console)
 	if (console == 0) {
 		if (c >= F_SCR && c <= MIN(L_SCR, F_SCR + VT_MAXWINDOWS - 1)) {
 			vw = vd->vd_windows[c - F_SCR];
-			if (vw != NULL)
-				vt_proc_window_switch(vw);
+			vt_proc_window_switch(vw);
 			return;
 		}
 		VT_LOCK(vd);
@@ -747,8 +769,7 @@ vt_processkey(keyboard_t *kbd, struct vt_device *vd, int c)
 
 		if (c >= F_SCR && c <= MIN(L_SCR, F_SCR + VT_MAXWINDOWS - 1)) {
 			vw = vd->vd_windows[c - F_SCR];
-			if (vw != NULL)
-				vt_proc_window_switch(vw);
+			vt_proc_window_switch(vw);
 			return (0);
 		}
 
@@ -757,15 +778,13 @@ vt_processkey(keyboard_t *kbd, struct vt_device *vd, int c)
 			/* Switch to next VT. */
 			c = (vw->vw_number + 1) % VT_MAXWINDOWS;
 			vw = vd->vd_windows[c];
-			if (vw != NULL)
-				vt_proc_window_switch(vw);
+			vt_proc_window_switch(vw);
 			return (0);
 		case PREV:
 			/* Switch to previous VT. */
-			c = (vw->vw_number - 1) % VT_MAXWINDOWS;
+			c = (vw->vw_number + VT_MAXWINDOWS - 1) % VT_MAXWINDOWS;
 			vw = vd->vd_windows[c];
-			if (vw != NULL)
-				vt_proc_window_switch(vw);
+			vt_proc_window_switch(vw);
 			return (0);
 		case SLK: {
 			vt_save_kbd_state(vw, kbd);
@@ -2702,8 +2721,7 @@ vt_resume(struct vt_device *vd)
 
 	if (vt_suspendswitch == 0)
 		return;
-	/* Switch back to saved window */
-	if (vd->vd_savedwindow != NULL)
-		vt_proc_window_switch(vd->vd_savedwindow);
+	/* Switch back to saved window, if any */
+	vt_proc_window_switch(vd->vd_savedwindow);
 	vd->vd_savedwindow = NULL;
 }
-- 
2.45.0