On Mon, Nov 08, 2021 at 03:24:39PM +0100, Borislav Petkov wrote:
I guess I can add another indirection to notifier_chain_register() and avoid touching all the call sites.
IOW, something like this below.
This way I won't have to touch all the callsites and the registration routines would still return a proper value instead of returning 0 unconditionally.
--- diff --git a/kernel/notifier.c b/kernel/notifier.c index b8251dc0bc0f..04f08b2ef17f 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -19,14 +19,12 @@ BLOCKING_NOTIFIER_HEAD(reboot_notifier_list); * are layered on top of these, with appropriate locking added. */
-static int notifier_chain_register(struct notifier_block **nl, - struct notifier_block *n) +static int __notifier_chain_register(struct notifier_block **nl, + struct notifier_block *n) { while ((*nl) != NULL) { - if (unlikely((*nl) == n)) { - WARN(1, "double register detected"); - return 0; - } + if (unlikely((*nl) == n)) + return -EEXIST; if (n->priority > (*nl)->priority) break; nl = &((*nl)->next); @@ -36,6 +34,18 @@ static int notifier_chain_register(struct notifier_block **nl, return 0; }
+static int notifier_chain_register(struct notifier_block **nl, + struct notifier_block *n) +{ + int ret = __notifier_chain_register(nl, n); + + if (ret == -EEXIST) + WARN(1, "double register of notifier callback %ps detected", + n->notifier_call); + + return ret; +} + static int notifier_chain_unregister(struct notifier_block **nl, struct notifier_block *n) {