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, 56 insertions, 0 deletions

diff --git a/net/wireless/tests/util.c b/net/wireless/tests/util.c
new file mode 100644
index 000000000..118f7fb42
--- /dev/null
+++ b/net/wireless/tests/util.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit fixture to have a (configurable) wiphy
+ *
+ * Copyright (C) 2023 Intel Corporation
+ */
+#include <linux/ieee80211.h>
+#include <net/cfg80211.h>
+#include <kunit/test.h>
+#include <kunit/test-bug.h>
+#include "util.h"
+
+int t_wiphy_init(struct kunit_resource *resource, void *ctx)
+{
+	struct kunit *test = kunit_get_current_test();
+	struct cfg80211_ops *ops;
+	struct wiphy *wiphy;
+	struct t_wiphy_priv *priv;
+
+	ops = kzalloc_obj(*ops);
+	KUNIT_ASSERT_NOT_NULL(test, ops);
+
+	wiphy = wiphy_new_nm(ops, sizeof(*priv), "kunit");
+	KUNIT_ASSERT_NOT_NULL(test, wiphy);
+
+	priv = wiphy_priv(wiphy);
+	priv->ctx = ctx;
+	priv->ops = ops;
+
+	/* Initialize channels, feel free to add more here channels/bands */
+	memcpy(priv->channels_2ghz, channels_2ghz, sizeof(channels_2ghz));
+	wiphy->bands[NL80211_BAND_2GHZ] = &priv->band_2ghz;
+	priv->band_2ghz.channels = priv->channels_2ghz;
+	priv->band_2ghz.n_channels = ARRAY_SIZE(channels_2ghz);
+
+	resource->data = wiphy;
+	resource->name = "wiphy";
+
+	return 0;
+}
+
+void t_wiphy_exit(struct kunit_resource *resource)
+{
+	struct t_wiphy_priv *priv;
+	struct cfg80211_ops *ops;
+
+	priv = wiphy_priv(resource->data);
+	ops = priv->ops;
+
+	/* Should we ensure anything about the state here?
+	 * e.g. full destruction or no calls to any ops on destruction?
+	 */
+
+	wiphy_free(resource->data);
+	kfree(ops);
+}