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, 92 insertions, 0 deletions

diff --git a/drivers/rtc/proc.c b/drivers/rtc/proc.c
new file mode 100644
index 000000000..cbcdbb19d
--- /dev/null
+++ b/drivers/rtc/proc.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RTC subsystem, proc interface
+ *
+ * Copyright (C) 2005-06 Tower Technologies
+ * Author: Alessandro Zummo <a.zummo@towertech.it>
+ *
+ * based on arch/arm/common/rtctime.c
+ */
+
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+
+#include "rtc-core.h"
+
+#define NAME_SIZE	10
+
+#if defined(CONFIG_RTC_HCTOSYS_DEVICE)
+static bool is_rtc_hctosys(struct rtc_device *rtc)
+{
+	int size;
+	char name[NAME_SIZE];
+
+	size = snprintf(name, NAME_SIZE, "rtc%d", rtc->id);
+	if (size >= NAME_SIZE)
+		return false;
+
+	return !strncmp(name, CONFIG_RTC_HCTOSYS_DEVICE, NAME_SIZE);
+}
+#else
+static bool is_rtc_hctosys(struct rtc_device *rtc)
+{
+	return (rtc->id == 0);
+}
+#endif
+
+static int rtc_proc_show(struct seq_file *seq, void *offset)
+{
+	int err;
+	struct rtc_device *rtc = seq->private;
+	const struct rtc_class_ops *ops = rtc->ops;
+	struct rtc_wkalrm alrm;
+	struct rtc_time tm;
+
+	err = rtc_read_time(rtc, &tm);
+	if (err == 0) {
+		seq_printf(seq,
+			   "rtc_time\t: %ptRt\n"
+			   "rtc_date\t: %ptRd\n",
+			   &tm, &tm);
+	}
+
+	err = rtc_read_alarm(rtc, &alrm);
+	if (err == 0) {
+		seq_printf(seq, "alrm_time\t: %ptRt\n", &alrm.time);
+		seq_printf(seq, "alrm_date\t: %ptRd\n", &alrm.time);
+		seq_printf(seq, "alarm_IRQ\t: %s\n",
+			   alrm.enabled ? "yes" : "no");
+		seq_printf(seq, "alrm_pending\t: %s\n",
+			   alrm.pending ? "yes" : "no");
+		seq_printf(seq, "update IRQ enabled\t: %s\n",
+			   (rtc->uie_rtctimer.enabled) ? "yes" : "no");
+		seq_printf(seq, "periodic IRQ enabled\t: %s\n",
+			   (rtc->pie_enabled) ? "yes" : "no");
+		seq_printf(seq, "periodic IRQ frequency\t: %d\n",
+			   rtc->irq_freq);
+		seq_printf(seq, "max user IRQ frequency\t: %d\n",
+			   rtc->max_user_freq);
+	}
+
+	seq_printf(seq, "24hr\t\t: yes\n");
+
+	if (ops->proc)
+		ops->proc(rtc->dev.parent, seq);
+
+	return 0;
+}
+
+void rtc_proc_add_device(struct rtc_device *rtc)
+{
+	if (is_rtc_hctosys(rtc))
+		proc_create_single_data("driver/rtc", 0, NULL, rtc_proc_show,
+					rtc);
+}
+
+void rtc_proc_del_device(struct rtc_device *rtc)
+{
+	if (is_rtc_hctosys(rtc))
+		remove_proc_entry("driver/rtc", NULL);
+}