patch 9.0.0192: possible invalid memory access when 'cmdheight' is zerov9.0.0192

Problem:    Possible invalid memory access when 'cmdheight' is zero. (Martin
            Tournoij)
Solution:   Avoid going over the end of w_lines[] when w_height is Rows.
            (closes #10882)

1 files changed, 5 insertions, 1 deletions

diff --git a/src/drawscreen.c b/src/drawscreen.c
index 578c66f2b9..a5822b25d8 100644
--- a/src/drawscreen.c
+++ b/src/drawscreen.c
@@ -1808,9 +1808,13 @@ win_update(win_T *wp)
 
 			    // Move the entries that were scrolled, disable
 			    // the entries for the lines to be redrawn.
+			    // Avoid using a wrong index when 'cmdheight' is
+			    // zero and wp->w_height == Rows.
 			    if ((wp->w_lines_valid += j) > wp->w_height)
 				wp->w_lines_valid = wp->w_height;
-			    for (idx = wp->w_lines_valid; idx - j >= 0; idx--)
+			    for (idx = wp->w_lines_valid >= wp->w_height
+				    ? wp->w_height - 1 : wp->w_lines_valid;
+							   idx - j >= 0; idx--)
 				wp->w_lines[idx] = wp->w_lines[idx - j];
 			    while (idx >= 0)
 				wp->w_lines[idx--].wl_valid = FALSE;