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, 110 insertions, 0 deletions

diff --git a/drivers/clk/tegra/clk-periph-fixed.c b/drivers/clk/tegra/clk-periph-fixed.c
new file mode 100644
index 000000000..bb33e32ca
--- /dev/null
+++ b/drivers/clk/tegra/clk-periph-fixed.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015, NVIDIA CORPORATION.  All rights reserved.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/io.h>
+
+#include "clk.h"
+
+static inline struct tegra_clk_periph_fixed *
+to_tegra_clk_periph_fixed(struct clk_hw *hw)
+{
+	return container_of(hw, struct tegra_clk_periph_fixed, hw);
+}
+
+static int tegra_clk_periph_fixed_is_enabled(struct clk_hw *hw)
+{
+	struct tegra_clk_periph_fixed *fixed = to_tegra_clk_periph_fixed(hw);
+	u32 mask = 1 << (fixed->num % 32), value;
+
+	value = readl(fixed->base + fixed->regs->enb_reg);
+	if (value & mask) {
+		value = readl(fixed->base + fixed->regs->rst_reg);
+		if ((value & mask) == 0)
+			return 1;
+	}
+
+	return 0;
+}
+
+static int tegra_clk_periph_fixed_enable(struct clk_hw *hw)
+{
+	struct tegra_clk_periph_fixed *fixed = to_tegra_clk_periph_fixed(hw);
+	u32 mask = 1 << (fixed->num % 32);
+
+	writel(mask, fixed->base + fixed->regs->enb_set_reg);
+
+	return 0;
+}
+
+static void tegra_clk_periph_fixed_disable(struct clk_hw *hw)
+{
+	struct tegra_clk_periph_fixed *fixed = to_tegra_clk_periph_fixed(hw);
+	u32 mask = 1 << (fixed->num % 32);
+
+	writel(mask, fixed->base + fixed->regs->enb_clr_reg);
+}
+
+static unsigned long
+tegra_clk_periph_fixed_recalc_rate(struct clk_hw *hw,
+				   unsigned long parent_rate)
+{
+	struct tegra_clk_periph_fixed *fixed = to_tegra_clk_periph_fixed(hw);
+	unsigned long long rate;
+
+	rate = (unsigned long long)parent_rate * fixed->mul;
+	do_div(rate, fixed->div);
+
+	return (unsigned long)rate;
+}
+
+static const struct clk_ops tegra_clk_periph_fixed_ops = {
+	.is_enabled = tegra_clk_periph_fixed_is_enabled,
+	.enable = tegra_clk_periph_fixed_enable,
+	.disable = tegra_clk_periph_fixed_disable,
+	.recalc_rate = tegra_clk_periph_fixed_recalc_rate,
+};
+
+struct clk *tegra_clk_register_periph_fixed(const char *name,
+					    const char *parent,
+					    unsigned long flags,
+					    void __iomem *base,
+					    unsigned int mul,
+					    unsigned int div,
+					    unsigned int num)
+{
+	const struct tegra_clk_periph_regs *regs;
+	struct tegra_clk_periph_fixed *fixed;
+	struct clk_init_data init;
+	struct clk *clk;
+
+	regs = get_reg_bank(num);
+	if (!regs)
+		return ERR_PTR(-EINVAL);
+
+	fixed = kzalloc_obj(*fixed);
+	if (!fixed)
+		return ERR_PTR(-ENOMEM);
+
+	init.name = name;
+	init.flags = flags;
+	init.parent_names = parent ? &parent : NULL;
+	init.num_parents = parent ? 1 : 0;
+	init.ops = &tegra_clk_periph_fixed_ops;
+
+	fixed->base = base;
+	fixed->regs = regs;
+	fixed->mul = mul;
+	fixed->div = div;
+	fixed->num = num;
+
+	fixed->hw.init = &init;
+
+	clk = clk_register(NULL, &fixed->hw);
+	if (IS_ERR(clk))
+		kfree(fixed);
+
+	return clk;
+}