fix(context): don't crash on invalid arg to nvim_get_context (#25977)

Note: The crash happens in the second test case when using uninitialized
memory, and therefore doesn't happen with ASAN.

src/nvim/api/private/converter.c

@@ -261,7 +261,9 @@ Object vim_to_object(typval_T *obj)
 /// @param obj  Object to convert from.
 /// @param tv   Conversion result is placed here. On failure member v_type is
 ///             set to VAR_UNKNOWN (no allocation was made for this variable).
-/// returns     true if conversion is successful, otherwise false.
+/// @param err  Error object.
+///
+/// @returns    true if conversion is successful, otherwise false.
 bool object_to_vim(Object obj, typval_T *tv, Error *err)
 {
   tv->v_type = VAR_UNKNOWN;

src/nvim/api/vim.c

@@ -1402,7 +1402,7 @@ Dictionary nvim_get_context(Dict(context) *opts, Error *err)
 /// Sets the current editor state from the given |context| map.
 ///
 /// @param  dict  |Context| map.
-Object nvim_load_context(Dictionary dict)
+Object nvim_load_context(Dictionary dict, Error *err)
   FUNC_API_SINCE(6)
 {
   Context ctx = CONTEXT_INIT;
@@ -1410,8 +1410,8 @@ Object nvim_load_context(Dictionary dict)
   int save_did_emsg = did_emsg;
   did_emsg = false;
 
-  ctx_from_dict(dict, &ctx);
-  if (!did_emsg) {
+  ctx_from_dict(dict, &ctx, err);
+  if (!ERROR_SET(err)) {
     ctx_restore(&ctx, kCtxAll);
   }
 

src/nvim/channel.c

@@ -224,6 +224,7 @@ void channel_create_event(Channel *chan, const char *ext_source)
   // TODO(bfredl): do the conversion in one step. Also would be nice
   // to pretty print top level dict in defined order
   (void)object_to_vim(DICTIONARY_OBJ(info), &tv, NULL);
+  assert(tv.v_type == VAR_DICT);
   char *str = encode_tv2json(&tv, NULL);
   ILOG("new channel %" PRIu64 " (%s) : %s", chan->id, source, str);
   xfree(str);
@@ -849,6 +850,7 @@ static void set_info_event(void **argv)
   Dictionary info = channel_info(chan->id);
   typval_T retval;
   (void)object_to_vim(DICTIONARY_OBJ(info), &retval, NULL);
+  assert(retval.v_type == VAR_DICT);
   tv_dict_add_dict(dict, S_LEN("info"), retval.vval.v_dict);
   tv_dict_set_keys_readonly(dict);
 

src/nvim/context.c

@@ -321,24 +321,28 @@ static inline Array sbuf_to_array(msgpack_sbuffer sbuf)
 /// Convert readfile()-style array to msgpack_sbuffer.
 ///
 /// @param[in]  array  readfile()-style array to convert.
+/// @param[out]  err   Error object.
 ///
 /// @return msgpack_sbuffer with conversion result.
-static inline msgpack_sbuffer array_to_sbuf(Array array)
+static inline msgpack_sbuffer array_to_sbuf(Array array, Error *err)
+  FUNC_ATTR_NONNULL_ALL
 {
   msgpack_sbuffer sbuf;
   msgpack_sbuffer_init(&sbuf);
 
   typval_T list_tv;
-  Error err = ERROR_INIT;
-  (void)object_to_vim(ARRAY_OBJ(array), &list_tv, &err);
+  if (!object_to_vim(ARRAY_OBJ(array), &list_tv, err)) {
+    return sbuf;
+  }
 
+  assert(list_tv.v_type == VAR_LIST);
   if (!encode_vim_list_to_buf(list_tv.vval.v_list, &sbuf.size, &sbuf.data)) {
-    emsg(_("E474: Failed to convert list to msgpack string buffer"));
+    api_set_error(err, kErrorTypeException, "%s",
+                  "E474: Failed to convert list to msgpack string buffer");
   }
   sbuf.alloc = sbuf.size;
 
   tv_clear(&list_tv);
-  api_clear_error(&err);
   return sbuf;
 }
 
@@ -367,9 +371,10 @@ Dictionary ctx_to_dict(Context *ctx)
 ///
 /// @param[in]   dict  Context Dictionary representation.
 /// @param[out]  ctx   Context object to store conversion result into.
+/// @param[out]  err   Error object.
 ///
 /// @return types of included context items.
-int ctx_from_dict(Dictionary dict, Context *ctx)
+int ctx_from_dict(Dictionary dict, Context *ctx, Error *err)
   FUNC_ATTR_NONNULL_ALL
 {
   assert(ctx != NULL);
@@ -382,16 +387,16 @@ int ctx_from_dict(Dictionary dict, Context *ctx)
     }
     if (strequal(item.key.data, "regs")) {
       types |= kCtxRegs;
-      ctx->regs = array_to_sbuf(item.value.data.array);
+      ctx->regs = array_to_sbuf(item.value.data.array, err);
     } else if (strequal(item.key.data, "jumps")) {
       types |= kCtxJumps;
-      ctx->jumps = array_to_sbuf(item.value.data.array);
+      ctx->jumps = array_to_sbuf(item.value.data.array, err);
     } else if (strequal(item.key.data, "bufs")) {
       types |= kCtxBufs;
-      ctx->bufs = array_to_sbuf(item.value.data.array);
+      ctx->bufs = array_to_sbuf(item.value.data.array, err);
     } else if (strequal(item.key.data, "gvars")) {
       types |= kCtxGVars;
-      ctx->gvars = array_to_sbuf(item.value.data.array);
+      ctx->gvars = array_to_sbuf(item.value.data.array, err);
     } else if (strequal(item.key.data, "funcs")) {
       types |= kCtxFuncs;
       ctx->funcs = copy_object(item.value, NULL).data.array;

src/nvim/eval/funcs.c

@@ -358,6 +358,7 @@ static void api_wrapper(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   }
 
   if (!object_to_vim(result, rettv, &err)) {
+    assert(ERROR_SET(&err));
     semsg(_("Error converting the call result: %s"), err.msg);
   }
 
@@ -1024,7 +1025,7 @@ static void f_ctxget(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
   Dictionary ctx_dict = ctx_to_dict(ctx);
   Error err = ERROR_INIT;
-  object_to_vim(DICTIONARY_OBJ(ctx_dict), rettv, &err);
+  (void)object_to_vim(DICTIONARY_OBJ(ctx_dict), rettv, &err);
   api_free_dictionary(ctx_dict);
   api_clear_error(&err);
 }
@@ -1090,14 +1091,16 @@ static void f_ctxset(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     return;
   }
 
-  int save_did_emsg = did_emsg;
+  const int save_did_emsg = did_emsg;
   did_emsg = false;
 
   Dictionary dict = vim_to_object(&argvars[0]).data.dictionary;
   Context tmp = CONTEXT_INIT;
-  ctx_from_dict(dict, &tmp);
+  Error err = ERROR_INIT;
+  ctx_from_dict(dict, &tmp, &err);
 
-  if (did_emsg) {
+  if (ERROR_SET(&err)) {
+    semsg("%s", err.msg);
     ctx_free(&tmp);
   } else {
     ctx_free(ctx);
@@ -1105,6 +1108,7 @@ static void f_ctxset(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   }
 
   api_free_dictionary(dict);
+  api_clear_error(&err);
   did_emsg = save_did_emsg;
 }
 
@@ -6753,6 +6757,7 @@ static void f_rpcrequest(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   }
 
   if (!object_to_vim(result, rettv, &err)) {
+    assert(ERROR_SET(&err));
     semsg(_("Error converting the call result: %s"), err.msg);
   }
 

test/functional/api/vim_spec.lua

@@ -1979,6 +1979,13 @@ describe('API', function()
       nvim('load_context', ctx)
       eq({1, 2 ,3}, eval('[g:one, g:Two, g:THREE]'))
     end)
+
+    it('errors when context dictionary is invalid', function()
+      eq('E474: Failed to convert list to msgpack string buffer',
+         pcall_err(nvim, 'load_context', { regs = { {} } }))
+      eq("Empty dictionary keys aren't allowed",
+         pcall_err(nvim, 'load_context', { regs = { { [''] = '' } } }))
+    end)
   end)
 
   describe('nvim_replace_termcodes', function()

test/functional/vimscript/ctx_functions_spec.lua

@@ -375,6 +375,12 @@ describe('context functions', function()
       eq(outofbounds, pcall_err(call, 'ctxset', {dummy = 1}, 0))
     end)
 
+    it('errors when context dictionary is invalid', function()
+      call('ctxpush')
+      eq('Vim:E474: Failed to convert list to msgpack string buffer',
+         pcall_err(call, 'ctxset', { regs = { {} } }))
+    end)
+
     it('sets context dictionary at index in context stack', function()
       nvim('set_var', 'one', 1)
       nvim('set_var', 'Two', 2)