vim-patch:9.0.0805: filetype autocmd may cause freed memory access

Problem:    Filetype autocmd may cause freed memory access.
Solution:   Set the quickfix-busy flag while filling the buffer.

d0fab10ed2

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/quickfix.c

@@ -3900,6 +3900,9 @@ static void qf_update_buffer(qf_info_T *qi, qfline_T *old_last)
       qf_winid = (int)win->handle;
     }
 
+    // autocommands may cause trouble
+    incr_quickfix_busy();
+
     aco_save_T aco;
 
     if (old_last == NULL) {
@@ -3924,6 +3927,9 @@ static void qf_update_buffer(qf_info_T *qi, qfline_T *old_last)
     if ((win = qf_find_win(qi)) != NULL && old_line_count < win->w_botline) {
       redraw_buf_later(buf, UPD_NOT_VALID);
     }
+
+    // always called after incr_quickfix_busy()
+    decr_quickfix_busy();
   }
 }
 

src/nvim/testdir/test_quickfix.vim

@@ -3298,6 +3298,21 @@ func Test_resize_from_copen()
   endtry
 endfunc
 
+func Test_filetype_autocmd()
+  " this changes the location list while it is in use to fill a buffer
+  lexpr ''
+  lopen
+  augroup FT_loclist
+    au FileType * call setloclist(0, [], 'f')
+  augroup END
+  silent! lolder
+  lexpr ''
+
+  augroup FT_loclist
+    au! FileType
+  augroup END
+endfunc
+
 func Test_vimgrep_with_textlock()
   new
 
@@ -6165,4 +6180,5 @@ func Test_loclist_replace_autocmd()
   call setloclist(0, [], 'f')
 endfunc
 
+
 " vim: shiftwidth=2 sts=2 expandtab