vt_ioctl: change VT_RESIZEX ioctl to check for error return from vc_resize()

vc_resize() can return with an error after failure. Change VT_RESIZEX ioctl
to save struct vc_data values that are modified and restore the original
values in case of error.

Signed-off-by: George Kennedy <george.kennedy@oracle.com>
Cc: stable <stable@vger.kernel.org>
Reported-by: syzbot+38a3699c7eaf165b97a6@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/1596213192-6635-2-git-send-email-george.kennedy@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 91c3017..a4e520b 100644 (file)
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -806,12 +806,22 @@ static int vt_resizex(struct vc_data *vc, struct vt_consize __user *cs)
                console_lock();
                vcp = vc_cons[i].d;
                if (vcp) {
+                       int ret;
+                       int save_scan_lines = vcp->vc_scan_lines;
+                       int save_font_height = vcp->vc_font.height;
+
                        if (v.v_vlin)
                                vcp->vc_scan_lines = v.v_vlin;
                        if (v.v_clin)
                                vcp->vc_font.height = v.v_clin;
                        vcp->vc_resize_user = 1;
-                       vc_resize(vcp, v.v_cols, v.v_rows);
+                       ret = vc_resize(vcp, v.v_cols, v.v_rows);
+                       if (ret) {
+                               vcp->vc_scan_lines = save_scan_lines;
+                               vcp->vc_font.height = save_font_height;
+                               console_unlock();
+                               return ret;
+                       }
                }
                console_unlock();
        }