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, 54 insertions, 0 deletions

diff --git a/arch/mips/rb532/time.c b/arch/mips/rb532/time.c
new file mode 100644
index 000000000..68713dd32
--- /dev/null
+++ b/arch/mips/rb532/time.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Carsten Langgaard, carstenl@mips.com
+ * Copyright (C) 1999,2000 MIPS Technologies, Inc.  All rights reserved.
+ *
+ *  Setting up the clock on the MIPS boards.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel_stat.h>
+#include <linux/ptrace.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/mc146818rtc.h>
+#include <linux/irq.h>
+#include <linux/timex.h>
+
+#include <asm/mipsregs.h>
+#include <asm/time.h>
+#include <asm/mach-rc32434/rc32434.h>
+
+extern unsigned int idt_cpu_freq;
+
+/*
+ * Figure out the r4k offset, the amount to increment the compare
+ * register for each time tick. There is no RTC available.
+ *
+ * The RC32434 counts at half the CPU *core* speed.
+ */
+static unsigned long __init cal_r4koff(void)
+{
+	mips_hpt_frequency = idt_cpu_freq * IDT_CLOCK_MULT / 2;
+
+	return mips_hpt_frequency / HZ;
+}
+
+void __init plat_time_init(void)
+{
+	unsigned int est_freq;
+	unsigned long flags, r4k_offset;
+
+	local_irq_save(flags);
+
+	printk(KERN_INFO "calculating r4koff... ");
+	r4k_offset = cal_r4koff();
+	printk("%08lx(%d)\n", r4k_offset, (int) r4k_offset);
+
+	est_freq = 2 * r4k_offset * HZ;
+	est_freq += 5000;	/* round */
+	est_freq -= est_freq % 10000;
+	printk(KERN_INFO "CPU frequency %d.%02d MHz\n", est_freq / 1000000,
+	       (est_freq % 1000000) * 100 / 1000000);
+	local_irq_restore(flags);
+}