vim-patch:9.1.1071: args missing after failing to redefine a function

Problem:  Arguments of a function are missing after failing to redefine
          it (after 8.2.2505), and heap-use-after-free with script-local
          function (after 9.1.1063).
Solution: Don't clear arguments or free uf_name_exp when failing to
          redefine an existing function (zeertzjq)

closes: vim/vim#16567

04d2a3fdc0

src/nvim/eval/userfunc.c

@@ -2825,11 +2825,11 @@ void ex_function(exarg_T *eap)
           && (fp->uf_script_ctx.sc_sid != current_sctx.sc_sid
               || fp->uf_script_ctx.sc_seq == current_sctx.sc_seq)) {
         emsg_funcname(e_funcexts, name);
-        goto erret;
+        goto errret_keep;
       }
       if (fp->uf_calls > 0) {
         emsg_funcname(N_("E127: Cannot redefine function %s: It is in use"), name);
-        goto erret;
+        goto errret_keep;
       }
       if (fp->uf_refcount > 1) {
         // This function is referenced somewhere, don't redefine it but
@@ -2961,9 +2961,6 @@ erret:
     ga_init(&fp->uf_def_args, (int)sizeof(char *), 1);
   }
 errret_2:
-  ga_clear_strings(&newargs);
-  ga_clear_strings(&default_args);
-  ga_clear_strings(&newlines);
   if (fp != NULL) {
     XFREE_CLEAR(fp->uf_name_exp);
   }
@@ -2971,6 +2968,10 @@ errret_2:
     xfree(fp);
     fp = NULL;
   }
+errret_keep:
+  ga_clear_strings(&newargs);
+  ga_clear_strings(&default_args);
+  ga_clear_strings(&newlines);
 ret_free:
   xfree(line_to_free);
   xfree(fudi.fd_newkey);

test/old/testdir/test_user_func.vim

@@ -421,12 +421,48 @@ func Test_func_def_error()
   call assert_fails('exe l', 'E717:')
 
   " Define an autoload function with an incorrect file name
-  call writefile(['func foo#Bar()', 'return 1', 'endfunc'], 'Xscript')
+  call writefile(['func foo#Bar()', 'return 1', 'endfunc'], 'Xscript', 'D')
   call assert_fails('source Xscript', 'E746:')
-  call delete('Xscript')
 
   " Try to list functions using an invalid search pattern
   call assert_fails('function /\%(/', 'E53:')
+
+  " Use a script-local function to cover uf_name_exp.
+  func s:TestRedefine(arg1 = 1, arg2 = 10)
+    let caught_E122 = 0
+    try
+      func s:TestRedefine(arg1 = 1, arg2 = 10)
+      endfunc
+    catch /E122:/
+      let caught_E122 = 1
+    endtry
+    call assert_equal(1, caught_E122)
+
+    let caught_E127 = 0
+    try
+      func! s:TestRedefine(arg1 = 1, arg2 = 10)
+      endfunc
+    catch /E127:/
+      let caught_E127 = 1
+    endtry
+    call assert_equal(1, caught_E127)
+
+    " The failures above shouldn't cause heap-use-after-free here.
+    return [a:arg1 + a:arg2, expand('<stack>')]
+  endfunc
+
+  let stacks = []
+  " Call the function twice.
+  " Failing to redefine a function shouldn't clear its argument list.
+  for i in range(2)
+    let [val, stack] = s:TestRedefine(1000)
+    call assert_equal(1010, val)
+    call assert_match(expand('<SID>') .. 'TestRedefine\[20\]$', stack)
+    call add(stacks, stack)
+  endfor
+  call assert_equal(stacks[0], stacks[1])
+
+  delfunc s:TestRedefine
 endfunc
 
 " Test for deleting a function