terminal: fix terminal attribute overflow

fixes #11548

src/nvim/screen.c

@@ -2692,8 +2692,8 @@ win_line (
     off += col;
   }
 
-  // wont highlight after 1024 columns
-  int term_attrs[1024] = {0};
+  // wont highlight after TERM_ATTRS_MAX columns
+  int term_attrs[TERM_ATTRS_MAX] = { 0 };
   if (wp->w_buffer->terminal) {
     terminal_get_line_attributes(wp->w_buffer->terminal, wp, lnum, term_attrs);
     extra_check = true;
@@ -4030,7 +4030,7 @@ win_line (
         int n = wp->w_p_rl ? -1 : 1;
         while (col >= 0 && col < grid->Columns) {
           schar_from_ascii(linebuf_char[off], ' ');
-          linebuf_attr[off] = term_attrs[vcol];
+          linebuf_attr[off] = vcol >= TERM_ATTRS_MAX ? 0 : term_attrs[vcol];
           off += n;
           vcol += n;
           col += n;

src/nvim/screen.h

@@ -32,6 +32,9 @@ EXTERN ScreenGrid default_grid INIT(= SCREEN_GRID_INIT);
 
 #define DEFAULT_GRID_HANDLE 1  // handle for the default_grid
 
+// Maximum columns for terminal highlight attributes
+#define TERM_ATTRS_MAX 1024
+
 /// Status line click definition
 typedef struct {
   enum {

src/nvim/terminal.c

@@ -588,6 +588,7 @@ void terminal_get_line_attributes(Terminal *term, win_T *wp, int linenr,
     return;
   }
 
+  width = MIN(TERM_ATTRS_MAX, width);
   for (int col = 0; col < width; col++) {
     VTermScreenCell cell;
     bool color_valid = fetch_cell(term, row, col, &cell);

test/functional/terminal/buffer_spec.lua

@@ -264,3 +264,12 @@ describe('No heap-buffer-overflow when using', function()
     feed_command('bdelete!')
   end)
 end)
+
+describe('No heap-buffer-overflow when', function()
+  it('set nowrap and send long line #11548', function()
+    feed_command('set nowrap')
+    feed_command('autocmd TermOpen * startinsert')
+    feed_command('call feedkeys("4000ai\\<esc>:terminal!\\<cr>")')
+    eq(2, eval('1+1'))
+  end)
+end)