From e1121b139480f53d1b06f84f3e4574048108fa0b Mon Sep 17 00:00:00 2001
From: Pavel Mayorov <pmayorov@cloudlinux.com>
Date: Mon, 20 Feb 2023 14:35:20 +0000
Subject: [PATCH] patch 9.0.1331: illegal memory access when using :ball in
 Visual mode

Problem:    Illegal memory access when using :ball in Visual mode.
Solution:   Stop Visual mode when using :ball. (Pavel Mayorov, closes #11923)
---
 src/buffer.c                |  4 ++++
 src/testdir/test_visual.vim | 19 +++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/src/buffer.c b/src/buffer.c
index cb7bdf445dee..ff35729fb929 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -5319,6 +5319,10 @@ ex_buffer_all(exarg_T *eap)
     else
 	all = TRUE;
 
+    // Stop Visual mode, the cursor and "VIsual" may very well be invalid after
+    // switching to another buffer.
+    reset_VIsual_and_resel();
+
     setpcmark();
 
 #ifdef FEAT_GUI
diff --git a/src/testdir/test_visual.vim b/src/testdir/test_visual.vim
index 295e16f93d9d..f152e7b79ba8 100644
--- a/src/testdir/test_visual.vim
+++ b/src/testdir/test_visual.vim
@@ -1493,5 +1493,24 @@ func Test_visual_area_adjusted_when_hiding()
   bwipe!
 endfunc
 
+" Check fix for the heap-based buffer overflow bug found in the function
+" utfc_ptr2len and reported at
+" https://huntr.dev/bounties/ae933869-a1ec-402a-bbea-d51764c6618e
+func Test_heap_buffer_overflow()
+  enew
+  set updatecount=0
+
+  norm R0
+  split other
+  norm R000
+  exe "norm \<C-V>l"
+  ball
+  call assert_equal(getpos("."), getpos("v"))
+  call assert_equal('n', mode())
+  norm zW
+
+  %bwipe!
+  set updatecount&
+endfunc

 " vim: shiftwidth=2 sts=2 expandtab
