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, 76 insertions, 0 deletions

diff --git a/drivers/clk/sprd/mux.c b/drivers/clk/sprd/mux.c
new file mode 100644
index 000000000..624041b60
--- /dev/null
+++ b/drivers/clk/sprd/mux.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Spreadtrum multiplexer clock driver
+//
+// Copyright (C) 2017 Spreadtrum, Inc.
+// Author: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/regmap.h>
+
+#include "mux.h"
+
+u8 sprd_mux_helper_get_parent(const struct sprd_clk_common *common,
+			      const struct sprd_mux_ssel *mux)
+{
+	unsigned int reg;
+	u8 parent;
+	int num_parents;
+	int i;
+
+	regmap_read(common->regmap, common->reg, &reg);
+	parent = reg >> mux->shift;
+	parent &= (1 << mux->width) - 1;
+
+	if (!mux->table)
+		return parent;
+
+	num_parents = clk_hw_get_num_parents(&common->hw);
+
+	for (i = 0; i < num_parents - 1; i++)
+		if (parent >= mux->table[i] && parent < mux->table[i + 1])
+			return i;
+
+	return num_parents - 1;
+}
+EXPORT_SYMBOL_GPL(sprd_mux_helper_get_parent);
+
+static u8 sprd_mux_get_parent(struct clk_hw *hw)
+{
+	struct sprd_mux *cm = hw_to_sprd_mux(hw);
+
+	return sprd_mux_helper_get_parent(&cm->common, &cm->mux);
+}
+
+int sprd_mux_helper_set_parent(const struct sprd_clk_common *common,
+			       const struct sprd_mux_ssel *mux,
+			       u8 index)
+{
+	unsigned int reg;
+
+	if (mux->table)
+		index = mux->table[index];
+
+	regmap_read(common->regmap, common->reg, &reg);
+	reg &= ~GENMASK(mux->width + mux->shift - 1, mux->shift);
+	regmap_write(common->regmap, common->reg,
+			  reg | (index << mux->shift));
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(sprd_mux_helper_set_parent);
+
+static int sprd_mux_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct sprd_mux *cm = hw_to_sprd_mux(hw);
+
+	return sprd_mux_helper_set_parent(&cm->common, &cm->mux, index);
+}
+
+const struct clk_ops sprd_mux_ops = {
+	.get_parent = sprd_mux_get_parent,
+	.set_parent = sprd_mux_set_parent,
+	.determine_rate = __clk_mux_determine_rate,
+};
+EXPORT_SYMBOL_GPL(sprd_mux_ops);