From a995b1e68129a0bb3928625c4f5a7bcb24893d75 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Petr=20=C5=A0tetiar?= Date: Mon, 16 Dec 2019 21:52:55 +0100 Subject: [PATCH] lua: workaround false positive dereference of null pointer MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit scan-build from clang-9 has reported following: ubus.c:837:16: warning: Access to field 'rnotify' results in a dereference of a null pointer (loaded from variable 'sub') sub->rnotify = luaL_ref(L, -2); Which is false positive as the lua_error() does a long jump and therefore never returns and this long jump probably confuses the static analyzer. So this patch workarounds this false positive by helping static analyzer by using common Lua idiom which is to return lua_error()'s return value. Ref: https://www.lua.org/manual/5.1/manual.html#lua_error Addresses-Coverity-ID: 1412355 ("Dereference after null check") Signed-off-by: Petr Å tetiar --- lua/ubus.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/lua/ubus.c b/lua/ubus.c index 6fbbc06..fb50418 100644 --- a/lua/ubus.c +++ b/lua/ubus.c @@ -557,8 +557,7 @@ static int ubus_lua_add(lua_State *L) /* verify top level object */ if (lua_istable(L, 1)) { lua_pushstring(L, "you need to pass a table"); - lua_error(L); - return 0; + return lua_error(L); } /* scan each object */ @@ -598,7 +597,7 @@ ubus_lua_notify( lua_State *L ) if( !lua_islightuserdata( L, 2 ) ){ lua_pushfstring( L, "Invald 2nd parameter, expected ubus obj ref" ); - lua_error( L ); + return lua_error( L ); } obj = lua_touserdata( L, 2 ); @@ -606,7 +605,7 @@ ubus_lua_notify( lua_State *L ) blob_buf_init(&c->buf, 0); if( !ubus_lua_format_blob_array( L, &c->buf, true ) ){ lua_pushfstring( L, "Invalid 4th parameter, expected table of arguments" ); - lua_error( L ); + return lua_error( L ); } ubus_notify( c->ctx, obj, method, c->buf.head, -1 ); @@ -812,7 +811,7 @@ ubus_sub_notify_handler(struct ubus_context *ctx, struct ubus_object *obj, -static void +static int ubus_lua_do_subscribe( struct ubus_context *ctx, lua_State *L, const char* target, int idxnotify, int idxremove ) { @@ -822,13 +821,13 @@ ubus_lua_do_subscribe( struct ubus_context *ctx, lua_State *L, const char* targe if( ( status = ubus_lookup_id( ctx, target, &id ) ) ){ lua_pushfstring( L, "Unable find target, status=%d", status ); - lua_error( L ); + return lua_error( L ); } sub = calloc( 1, sizeof( struct ubus_lua_subscriber ) ); if( !sub ){ lua_pushstring( L, "Out of memory" ); - lua_error( L ); + return lua_error( L ); } if( idxnotify ){ @@ -849,13 +848,15 @@ ubus_lua_do_subscribe( struct ubus_context *ctx, lua_State *L, const char* targe if( ( status = ubus_register_subscriber( ctx, &sub->s ) ) ){ lua_pushfstring( L, "Failed to register subscriber, status=%d", status ); - lua_error( L ); + return lua_error( L ); } if( ( status = ubus_subscribe( ctx, &sub->s, id) ) ){ lua_pushfstring( L, "Failed to register subscriber, status=%d", status ); - lua_error( L ); + return lua_error( L ); } + + return 0; } static int -- 2.25.1