bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/net/dcb/dcbevent.c b/net/dcb/dcbevent.c
new file mode 100644
index 000000000..8620564c2
--- /dev/null
+++ b/net/dcb/dcbevent.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2010, Intel Corporation.
+ *
+ * Author: John Fastabend <john.r.fastabend@intel.com>
+ */
+
+#include <linux/rtnetlink.h>
+#include <linux/notifier.h>
+#include <linux/export.h>
+#include <net/dcbevent.h>
+
+static ATOMIC_NOTIFIER_HEAD(dcbevent_notif_chain);
+
+int register_dcbevent_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_register(&dcbevent_notif_chain, nb);
+}
+EXPORT_SYMBOL(register_dcbevent_notifier);
+
+int unregister_dcbevent_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_unregister(&dcbevent_notif_chain, nb);
+}
+EXPORT_SYMBOL(unregister_dcbevent_notifier);
+
+int call_dcbevent_notifiers(unsigned long val, void *v)
+{
+	return atomic_notifier_call_chain(&dcbevent_notif_chain, val, v);
+}