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, 189 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-milbeaut.c b/drivers/clocksource/timer-milbeaut.c
new file mode 100644
index 000000000..fa9fb4eac
--- /dev/null
+++ b/drivers/clocksource/timer-milbeaut.c
@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018 Socionext Inc.
+ */
+
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/irqreturn.h>
+#include <linux/sched_clock.h>
+#include "timer-of.h"
+
+#define MLB_TMR_TMCSR_OFS	0x0
+#define MLB_TMR_TMR_OFS		0x4
+#define MLB_TMR_TMRLR1_OFS	0x8
+#define MLB_TMR_TMRLR2_OFS	0xc
+#define MLB_TMR_REGSZPCH	0x10
+
+#define MLB_TMR_TMCSR_OUTL	BIT(5)
+#define MLB_TMR_TMCSR_RELD	BIT(4)
+#define MLB_TMR_TMCSR_INTE	BIT(3)
+#define MLB_TMR_TMCSR_UF	BIT(2)
+#define MLB_TMR_TMCSR_CNTE	BIT(1)
+#define MLB_TMR_TMCSR_TRG	BIT(0)
+
+#define MLB_TMR_TMCSR_CSL_DIV2	0
+#define MLB_TMR_DIV_CNT		2
+
+#define MLB_TMR_SRC_CH		1
+#define MLB_TMR_EVT_CH		0
+
+#define MLB_TMR_SRC_CH_OFS	(MLB_TMR_REGSZPCH * MLB_TMR_SRC_CH)
+#define MLB_TMR_EVT_CH_OFS	(MLB_TMR_REGSZPCH * MLB_TMR_EVT_CH)
+
+#define MLB_TMR_SRC_TMCSR_OFS	(MLB_TMR_SRC_CH_OFS + MLB_TMR_TMCSR_OFS)
+#define MLB_TMR_SRC_TMR_OFS	(MLB_TMR_SRC_CH_OFS + MLB_TMR_TMR_OFS)
+#define MLB_TMR_SRC_TMRLR1_OFS	(MLB_TMR_SRC_CH_OFS + MLB_TMR_TMRLR1_OFS)
+#define MLB_TMR_SRC_TMRLR2_OFS	(MLB_TMR_SRC_CH_OFS + MLB_TMR_TMRLR2_OFS)
+
+#define MLB_TMR_EVT_TMCSR_OFS	(MLB_TMR_EVT_CH_OFS + MLB_TMR_TMCSR_OFS)
+#define MLB_TMR_EVT_TMR_OFS	(MLB_TMR_EVT_CH_OFS + MLB_TMR_TMR_OFS)
+#define MLB_TMR_EVT_TMRLR1_OFS	(MLB_TMR_EVT_CH_OFS + MLB_TMR_TMRLR1_OFS)
+#define MLB_TMR_EVT_TMRLR2_OFS	(MLB_TMR_EVT_CH_OFS + MLB_TMR_TMRLR2_OFS)
+
+#define MLB_TIMER_RATING	500
+#define MLB_TIMER_ONESHOT	0
+#define MLB_TIMER_PERIODIC	1
+
+static irqreturn_t mlb_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *clk = dev_id;
+	struct timer_of *to = to_timer_of(clk);
+	u32 val;
+
+	val = readl_relaxed(timer_of_base(to) + MLB_TMR_EVT_TMCSR_OFS);
+	val &= ~MLB_TMR_TMCSR_UF;
+	writel_relaxed(val, timer_of_base(to) + MLB_TMR_EVT_TMCSR_OFS);
+
+	clk->event_handler(clk);
+
+	return IRQ_HANDLED;
+}
+
+static void mlb_evt_timer_start(struct timer_of *to, bool periodic)
+{
+	u32 val = MLB_TMR_TMCSR_CSL_DIV2;
+
+	val |= MLB_TMR_TMCSR_CNTE | MLB_TMR_TMCSR_TRG | MLB_TMR_TMCSR_INTE;
+	if (periodic)
+		val |= MLB_TMR_TMCSR_RELD;
+	writel_relaxed(val, timer_of_base(to) + MLB_TMR_EVT_TMCSR_OFS);
+}
+
+static void mlb_evt_timer_stop(struct timer_of *to)
+{
+	u32 val = readl_relaxed(timer_of_base(to) + MLB_TMR_EVT_TMCSR_OFS);
+
+	val &= ~MLB_TMR_TMCSR_CNTE;
+	writel_relaxed(val, timer_of_base(to) + MLB_TMR_EVT_TMCSR_OFS);
+}
+
+static void mlb_evt_timer_register_count(struct timer_of *to, unsigned long cnt)
+{
+	writel_relaxed(cnt, timer_of_base(to) + MLB_TMR_EVT_TMRLR1_OFS);
+}
+
+static int mlb_set_state_periodic(struct clock_event_device *clk)
+{
+	struct timer_of *to = to_timer_of(clk);
+
+	mlb_evt_timer_stop(to);
+	mlb_evt_timer_register_count(to, to->of_clk.period);
+	mlb_evt_timer_start(to, MLB_TIMER_PERIODIC);
+	return 0;
+}
+
+static int mlb_set_state_oneshot(struct clock_event_device *clk)
+{
+	struct timer_of *to = to_timer_of(clk);
+
+	mlb_evt_timer_stop(to);
+	mlb_evt_timer_start(to, MLB_TIMER_ONESHOT);
+	return 0;
+}
+
+static int mlb_set_state_shutdown(struct clock_event_device *clk)
+{
+	struct timer_of *to = to_timer_of(clk);
+
+	mlb_evt_timer_stop(to);
+	return 0;
+}
+
+static int mlb_clkevt_next_event(unsigned long event,
+				   struct clock_event_device *clk)
+{
+	struct timer_of *to = to_timer_of(clk);
+
+	mlb_evt_timer_stop(to);
+	mlb_evt_timer_register_count(to, event);
+	mlb_evt_timer_start(to, MLB_TIMER_ONESHOT);
+	return 0;
+}
+
+static int mlb_config_clock_source(struct timer_of *to)
+{
+	u32 val = MLB_TMR_TMCSR_CSL_DIV2;
+
+	writel_relaxed(val, timer_of_base(to) + MLB_TMR_SRC_TMCSR_OFS);
+	writel_relaxed(~0, timer_of_base(to) + MLB_TMR_SRC_TMRLR1_OFS);
+	writel_relaxed(~0, timer_of_base(to) + MLB_TMR_SRC_TMRLR2_OFS);
+	val |= MLB_TMR_TMCSR_RELD | MLB_TMR_TMCSR_CNTE | MLB_TMR_TMCSR_TRG;
+	writel_relaxed(val, timer_of_base(to) + MLB_TMR_SRC_TMCSR_OFS);
+	return 0;
+}
+
+static int mlb_config_clock_event(struct timer_of *to)
+{
+	writel_relaxed(0, timer_of_base(to) + MLB_TMR_EVT_TMCSR_OFS);
+	return 0;
+}
+
+static struct timer_of to = {
+	.flags = TIMER_OF_IRQ | TIMER_OF_BASE | TIMER_OF_CLOCK,
+
+	.clkevt = {
+		.name = "mlb-clkevt",
+		.rating = MLB_TIMER_RATING,
+		.cpumask = cpu_possible_mask,
+		.features = CLOCK_EVT_FEAT_DYNIRQ | CLOCK_EVT_FEAT_ONESHOT,
+		.set_state_oneshot = mlb_set_state_oneshot,
+		.set_state_periodic = mlb_set_state_periodic,
+		.set_state_shutdown = mlb_set_state_shutdown,
+		.set_next_event = mlb_clkevt_next_event,
+	},
+
+	.of_irq = {
+		.flags = IRQF_TIMER | IRQF_IRQPOLL,
+		.handler = mlb_timer_interrupt,
+	},
+};
+
+static u64 notrace mlb_timer_sched_read(void)
+{
+	return ~readl_relaxed(timer_of_base(&to) + MLB_TMR_SRC_TMR_OFS);
+}
+
+static int __init mlb_timer_init(struct device_node *node)
+{
+	int ret;
+	unsigned long rate;
+
+	ret = timer_of_init(node, &to);
+	if (ret)
+		return ret;
+
+	rate = timer_of_rate(&to) / MLB_TMR_DIV_CNT;
+	mlb_config_clock_source(&to);
+	clocksource_mmio_init(timer_of_base(&to) + MLB_TMR_SRC_TMR_OFS,
+		node->name, rate, MLB_TIMER_RATING, 32,
+		clocksource_mmio_readl_down);
+	sched_clock_register(mlb_timer_sched_read, 32, rate);
+	mlb_config_clock_event(&to);
+	clockevents_config_and_register(&to.clkevt, timer_of_rate(&to), 15,
+		0xffffffff);
+	return 0;
+}
+TIMER_OF_DECLARE(mlb_peritimer, "socionext,milbeaut-timer",
+		mlb_timer_init);