selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 75 insertions, 0 deletions

diff --git a/drivers/clk/tegra/clk-audio-sync.c b/drivers/clk/tegra/clk-audio-sync.c
new file mode 100644
index 000000000..0bbfcf46b
--- /dev/null
+++ b/drivers/clk/tegra/clk-audio-sync.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+
+#include "clk.h"
+
+static unsigned long clk_sync_source_recalc_rate(struct clk_hw *hw,
+						 unsigned long parent_rate)
+{
+	struct tegra_clk_sync_source *sync = to_clk_sync_source(hw);
+
+	return sync->rate;
+}
+
+static int clk_sync_source_determine_rate(struct clk_hw *hw,
+					  struct clk_rate_request *req)
+{
+	struct tegra_clk_sync_source *sync = to_clk_sync_source(hw);
+
+	if (req->rate > sync->max_rate)
+		return -EINVAL;
+	else
+		return 0;
+}
+
+static int clk_sync_source_set_rate(struct clk_hw *hw, unsigned long rate,
+				    unsigned long parent_rate)
+{
+	struct tegra_clk_sync_source *sync = to_clk_sync_source(hw);
+
+	sync->rate = rate;
+	return 0;
+}
+
+const struct clk_ops tegra_clk_sync_source_ops = {
+	.determine_rate = clk_sync_source_determine_rate,
+	.set_rate = clk_sync_source_set_rate,
+	.recalc_rate = clk_sync_source_recalc_rate,
+};
+
+struct clk *tegra_clk_register_sync_source(const char *name,
+					   unsigned long max_rate)
+{
+	struct tegra_clk_sync_source *sync;
+	struct clk_init_data init;
+	struct clk *clk;
+
+	sync = kzalloc_obj(*sync);
+	if (!sync) {
+		pr_err("%s: could not allocate sync source clk\n", __func__);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	sync->max_rate = max_rate;
+
+	init.ops = &tegra_clk_sync_source_ops;
+	init.name = name;
+	init.flags = 0;
+	init.parent_names = NULL;
+	init.num_parents = 0;
+
+	/* Data in .init is copied by clk_register(), so stack variable OK */
+	sync->hw.init = &init;
+
+	clk = clk_register(NULL, &sync->hw);
+	if (IS_ERR(clk))
+		kfree(sync);
+
+	return clk;
+}