patch 9.0.0614: SpellFileMissing autocmd may delete buffer

Problem:    SpellFileMissing autocmd may delete buffer.
Solution:   Disallow deleting the current buffer to avoid using freed memory.

src/buffer.c

@@ -468,7 +468,12 @@ can_unload_buffer(buf_T *buf)
 	    }
     }
     if (!can_unload)
-	semsg(_(e_attempt_to_delete_buffer_that_is_in_use_str), buf->b_fname);
+    {
+	char_u *fname = buf->b_fname != NULL ? buf->b_fname : buf->b_ffname;
+
+	semsg(_(e_attempt_to_delete_buffer_that_is_in_use_str),
+				fname != NULL ? fname : (char_u *)"[No Name]");
+    }
     return can_unload;
 }
 

src/spell.c

@@ -1568,6 +1568,10 @@ spell_load_lang(char_u *lang)
     sl.sl_slang = NULL;
     sl.sl_nobreak = FALSE;
 
+    // Disallow deleting the current buffer.  Autocommands can do weird things
+    // and cause "lang" to be freed.
+    ++curbuf->b_locked;
+
     // We may retry when no spell file is found for the language, an
     // autocommand may load it then.
     for (round = 1; round <= 2; ++round)
@@ -1621,6 +1625,8 @@ spell_load_lang(char_u *lang)
 	STRCPY(fname_enc + STRLEN(fname_enc) - 3, "add.spl");
 	do_in_runtimepath(fname_enc, DIP_ALL, spell_load_cb, &sl);
     }
+
+    --curbuf->b_locked;
 }
 
 /*

src/testdir/test_autocmd.vim

@@ -2880,6 +2880,16 @@ func Test_FileType_spell()
   setglobal spellfile=
 endfunc
 
+" this was wiping out the current buffer and using freed memory
+func Test_SpellFileMissing_bwipe()
+  next 0
+  au SpellFileMissing 0 bwipe
+  call assert_fails('set spell spelllang=0', 'E937:')
+
+  au! SpellFileMissing
+  bwipe
+endfunc
+
 " Test closing a window or editing another buffer from a FileChangedRO handler
 " in a readonly buffer
 func Test_FileChangedRO_winclose()

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    614,
 /**/
     613,
 /**/