From 550667a9ea9edcec3071a1d7ec7c868aa7c791ad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Tue, 19 May 2020 18:47:38 +0200
Subject: [PATCH] term: scrolling: calling function must clamp scroll amount

---
 csi.c      | 16 ++++++++++++----
 terminal.c |  8 ++++----
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/csi.c b/csi.c
index eb188656..56346e6e 100644
--- a/csi.c
+++ b/csi.c
@@ -650,13 +650,21 @@ csi_dispatch(struct terminal *term, uint8_t final)
             break;
         }
 
-        case 'S':
-            term_scroll(term, vt_param_get(term, 0, 1));
+        case 'S': {
+            int amount = min(
+                vt_param_get(term, 0, 1),
+                term->scroll_region.end - term->scroll_region.start);
+            term_scroll(term, amount);
             break;
+        }
 
-        case 'T':
-            term_scroll_reverse(term, vt_param_get(term, 0, 1));
+        case 'T': {
+            int amount = min(
+                vt_param_get(term, 0, 1),
+                term->scroll_region.end - term->scroll_region.start);
+            term_scroll_reverse(term, amount);
             break;
+        }
 
         case 'X': {
             /* Erase chars */
diff --git a/terminal.c b/terminal.c
index 2bb94338..5dd29aa0 100644
--- a/terminal.c
+++ b/terminal.c
@@ -1744,8 +1744,8 @@ term_scroll_partial(struct terminal *term, struct scroll_region region, int rows
     LOG_DBG("scroll: rows=%d, region.start=%d, region.end=%d",
             rows, region.start, region.end);
 
-    /* Clamp scroll amount */
-    rows = min(rows, region.end - region.start);
+    /* Verify scroll amount has been clamped */
+    assert(rows <= region.end - region.start);
 
     /* Cancel selections that cannot be scrolled */
     if (unlikely(term->selection.start.row != -1)) {
@@ -1816,8 +1816,8 @@ term_scroll_reverse_partial(struct terminal *term,
     LOG_DBG("scroll reverse: rows=%d, region.start=%d, region.end=%d",
             rows, region.start, region.end);
 
-    /* Clamp scroll amount */
-    rows = min(rows, region.end - region.start);
+    /* Verify scroll amount has been clamped */
+    assert(rows <= region.end - region.start);
 
     /* Cancel selections that cannot be scrolled */
     if (unlikely(term->selection.start.row != -1)) {