diff --git a/fs/coredump.c b/fs/coredump.c
index d25bad2ed061..5c0375e7440f 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -788,6 +788,14 @@ void do_coredump(const kernel_siginfo_t *siginfo)
 	if (displaced)
 		put_files_struct(displaced);
 	if (!dump_interrupted()) {
+		/*
+		 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
+		 * have this set to NULL.
+		 */
+		if (!cprm.file) {
+			pr_info("Core dump to |%s disabled\n", cn.corename);
+			goto close_fail;
+		}
 		file_start_write(cprm.file);
 		core_dumped = binfmt->core_dump(&cprm);
 		file_end_write(cprm.file);
diff --git a/kernel/umh.c b/kernel/umh.c
index 7f255b5a8845..11bf5eea474c 100644
--- a/kernel/umh.c
+++ b/kernel/umh.c
@@ -544,6 +544,11 @@ EXPORT_SYMBOL_GPL(fork_usermode_blob);
  * Runs a user-space application.  The application is started
  * asynchronously if wait is not set, and runs as a child of system workqueues.
  * (ie. it runs with full root capabilities and optimized affinity).
+ *
+ * Note: successful return value does not guarantee the helper was called at
+ * all. You can't rely on sub_info->{init,cleanup} being called even for
+ * UMH_WAIT_* wait modes as STATIC_USERMODEHELPER_PATH="" turns all helpers
+ * into a successful no-op.
  */
 int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 {