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, 144 insertions, 0 deletions

diff --git a/drivers/acpi/ec_sys.c b/drivers/acpi/ec_sys.c
new file mode 100644
index 000000000..c074a0fae
--- /dev/null
+++ b/drivers/acpi/ec_sys.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ec_sys.c
+ *
+ * Copyright (C) 2010 SUSE Products GmbH/Novell
+ * Author:
+ *      Thomas Renninger <trenn@suse.de>
+ */
+
+#include <linux/kernel.h>
+#include <linux/acpi.h>
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include "internal.h"
+
+MODULE_AUTHOR("Thomas Renninger <trenn@suse.de>");
+MODULE_DESCRIPTION("ACPI EC sysfs access driver");
+MODULE_LICENSE("GPL");
+
+static bool write_support;
+module_param_hw(write_support, bool, other, 0644);
+MODULE_PARM_DESC(write_support, "Dangerous, reboot and removal of battery may "
+		 "be needed.");
+
+#define EC_SPACE_SIZE 256
+
+static struct dentry *acpi_ec_debugfs_dir;
+
+static ssize_t acpi_ec_read_io(struct file *f, char __user *buf,
+			       size_t count, loff_t *off)
+{
+	/* Use this if support reading/writing multiple ECs exists in ec.c:
+	 * struct acpi_ec *ec = ((struct seq_file *)f->private_data)->private;
+	 */
+	unsigned int size = EC_SPACE_SIZE;
+	loff_t init_off = *off;
+	int err = 0;
+
+	if (*off >= size)
+		return 0;
+	if (*off + count >= size) {
+		size -= *off;
+		count = size;
+	} else
+		size = count;
+
+	while (size) {
+		u8 byte_read;
+		err = ec_read(*off, &byte_read);
+		if (err)
+			return err;
+		if (put_user(byte_read, buf + *off - init_off)) {
+			if (*off - init_off)
+				return *off - init_off; /* partial read */
+			return -EFAULT;
+		}
+		*off += 1;
+		size--;
+	}
+	return count;
+}
+
+static ssize_t acpi_ec_write_io(struct file *f, const char __user *buf,
+				size_t count, loff_t *off)
+{
+	/* Use this if support reading/writing multiple ECs exists in ec.c:
+	 * struct acpi_ec *ec = ((struct seq_file *)f->private_data)->private;
+	 */
+
+	unsigned int size = count;
+	loff_t init_off = *off;
+	int err = 0;
+
+	if (!write_support)
+		return -EINVAL;
+
+	if (*off >= EC_SPACE_SIZE)
+		return 0;
+	if (*off + count >= EC_SPACE_SIZE) {
+		size = EC_SPACE_SIZE - *off;
+		count = size;
+	}
+
+	while (size) {
+		u8 byte_write;
+		if (get_user(byte_write, buf + *off - init_off)) {
+			if (*off - init_off)
+				return *off - init_off; /* partial write */
+			return -EFAULT;
+		}
+		err = ec_write(*off, byte_write);
+		if (err)
+			return err;
+
+		*off += 1;
+		size--;
+	}
+	return count;
+}
+
+static const struct file_operations acpi_ec_io_ops = {
+	.owner = THIS_MODULE,
+	.open  = simple_open,
+	.read  = acpi_ec_read_io,
+	.write = acpi_ec_write_io,
+	.llseek = default_llseek,
+};
+
+static void acpi_ec_add_debugfs(struct acpi_ec *ec, unsigned int ec_device_count)
+{
+	struct dentry *dev_dir;
+	char name[64];
+	umode_t mode = 0400;
+
+	if (ec_device_count == 0)
+		acpi_ec_debugfs_dir = debugfs_create_dir("ec", NULL);
+
+	sprintf(name, "ec%u", ec_device_count);
+	dev_dir = debugfs_create_dir(name, acpi_ec_debugfs_dir);
+
+	debugfs_create_x32("gpe", 0444, dev_dir, &first_ec->gpe);
+	debugfs_create_bool("use_global_lock", 0444, dev_dir,
+			    &first_ec->global_lock);
+
+	if (write_support)
+		mode = 0600;
+	debugfs_create_file("io", mode, dev_dir, ec, &acpi_ec_io_ops);
+}
+
+static int __init acpi_ec_sys_init(void)
+{
+	if (first_ec)
+		acpi_ec_add_debugfs(first_ec, 0);
+	return 0;
+}
+
+static void __exit acpi_ec_sys_exit(void)
+{
+	debugfs_remove_recursive(acpi_ec_debugfs_dir);
+}
+
+module_init(acpi_ec_sys_init);
+module_exit(acpi_ec_sys_exit);