VT_RESIZEX: get rid of field-by-field copyin

BugLink: https://bugs.launchpad.net/bugs/1868627

[ Upstream commit 1b3bce4d ]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

drivers/tty/vt/vt_ioctl.c

@@ -850,58 +850,44 @@ int vt_ioctl(struct tty_struct *tty,
 
 	case VT_RESIZEX:
 	{
-		struct vt_consize __user *vtconsize = up;
-		ushort ll,cc,vlin,clin,vcol,ccol;
+		struct vt_consize v;
 		if (!perm)
 			return -EPERM;
-		if (!access_ok(VERIFY_READ, vtconsize,
-				sizeof(struct vt_consize))) {
-			ret = -EFAULT;
-			break;
-		}
+		if (copy_from_user(&v, up, sizeof(struct vt_consize)))
+			return -EFAULT;
 		/* FIXME: Should check the copies properly */
-		__get_user(ll, &vtconsize->v_rows);
-		__get_user(cc, &vtconsize->v_cols);
-		__get_user(vlin, &vtconsize->v_vlin);
-		__get_user(clin, &vtconsize->v_clin);
-		__get_user(vcol, &vtconsize->v_vcol);
-		__get_user(ccol, &vtconsize->v_ccol);
-		vlin = vlin ? vlin : vc->vc_scan_lines;
-		if (clin) {
-			if (ll) {
-				if (ll != vlin/clin) {
-					/* Parameters don't add up */
-					ret = -EINVAL;
-					break;
-				}
-			} else 
-				ll = vlin/clin;
+		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 (vcol && ccol) {
-			if (cc) {
-				if (cc != vcol/ccol) {
-					ret = -EINVAL;
-					break;
-				}
-			} else
-				cc = vcol/ccol;
+		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 (clin > 32) {
-			ret =  -EINVAL;
-			break;
-		}
-		    
+		if (v.v_clin > 32)
+			return -EINVAL;
+
 		for (i = 0; i < MAX_NR_CONSOLES; i++) {
 			if (!vc_cons[i].d)
 				continue;
 			console_lock();
-			if (vlin)
-				vc_cons[i].d->vc_scan_lines = vlin;
-			if (clin)
-				vc_cons[i].d->vc_font.height = clin;
+			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, cc, ll);
+			vc_resize(vc_cons[i].d, v.v_cols, v.v_rows);
 			console_unlock();
 		}
 		break;