try to fix

Signed-off-by: Mykyta Yatsenko <[email protected]>

Author: mykyta5

kernel/bpf/helpers.c

@@ -1348,7 +1348,7 @@ static int __bpf_async_init(struct bpf_async_kern *async, struct bpf_map *map, u
 		/* maps with timers must be either held by user space
 		 * or pinned in bpffs.
 		 */
-		switch (type) {
+		switch (type) { //TODO: async may already have another cb attached
 		case BPF_ASYNC_TYPE_TIMER:
 			bpf_timer_cancel_and_free(async);
 			break;
@@ -1452,15 +1452,19 @@ static int __bpf_async_set_callback(struct bpf_async_kern *async, void *callback
 {
 	struct bpf_prog *prog = aux->prog;
 	struct bpf_async_cb *cb;
+	int ret;
 
 	if (in_nmi())
 		return -EOPNOTSUPP;
 
+	guard(rcu)();
+
 	cb = READ_ONCE(async->cb);
 	if (!cb)
 		return -EINVAL;
 
-	return bpf_async_update_callback(cb, callback_fn, prog);
+	ret = bpf_async_update_callback(cb, callback_fn, prog);
+	return ret;
 }
 
 BPF_CALL_3(bpf_timer_set_callback, struct bpf_async_kern *, timer, void *, callback_fn,