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, 90 insertions, 0 deletions

diff --git a/arch/m68k/mac/baboon.c b/arch/m68k/mac/baboon.c
new file mode 100644
index 000000000..5c97a7058
--- /dev/null
+++ b/arch/m68k/mac/baboon.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Baboon Custom IC Management
+ *
+ * The Baboon custom IC controls the IDE, PCMCIA and media bay on the
+ * PowerBook 190. It multiplexes multiple interrupt sources onto the
+ * Nubus slot $C interrupt.
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/irq.h>
+
+#include <asm/macintosh.h>
+#include <asm/macints.h>
+#include <asm/mac_baboon.h>
+
+#include "mac.h"
+
+int baboon_present;
+static volatile struct baboon *baboon;
+
+/*
+ * Baboon initialization.
+ */
+
+void __init baboon_init(void)
+{
+	if (macintosh_config->ident != MAC_MODEL_PB190) {
+		baboon = NULL;
+		baboon_present = 0;
+		return;
+	}
+
+	baboon = (struct baboon *) BABOON_BASE;
+	baboon_present = 1;
+
+	pr_debug("Baboon detected at %p\n", baboon);
+}
+
+/*
+ * Baboon interrupt handler.
+ * XXX how do you clear a pending IRQ? is it even necessary?
+ */
+
+static void baboon_irq(struct irq_desc *desc)
+{
+	short events, irq_bit;
+	int irq_num;
+
+	events = baboon->mb_ifr & 0x07;
+	irq_num = IRQ_BABOON_0;
+	irq_bit = 1;
+	do {
+		if (events & irq_bit) {
+			events &= ~irq_bit;
+			generic_handle_irq(irq_num);
+		}
+		++irq_num;
+		irq_bit <<= 1;
+	} while (events);
+}
+
+/*
+ * Register the Baboon interrupt dispatcher on nubus slot $C.
+ */
+
+void __init baboon_register_interrupts(void)
+{
+	irq_set_chained_handler(IRQ_NUBUS_C, baboon_irq);
+}
+
+/*
+ * The means for masking individual Baboon interrupts remains a mystery.
+ * However, since we only use the IDE IRQ, we can just enable/disable all
+ * Baboon interrupts. If/when we handle more than one Baboon IRQ, we must
+ * either figure out how to mask them individually or else implement the
+ * same workaround that's used for NuBus slots (see nubus_disabled and
+ * via_nubus_irq_shutdown).
+ */
+
+void baboon_irq_enable(int irq)
+{
+	mac_irq_enable(irq_get_irq_data(IRQ_NUBUS_C));
+}
+
+void baboon_irq_disable(int irq)
+{
+	mac_irq_disable(irq_get_irq_data(IRQ_NUBUS_C));
+}