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, 96 insertions, 0 deletions

diff --git a/drivers/mfd/rdc321x-southbridge.c b/drivers/mfd/rdc321x-southbridge.c
new file mode 100644
index 000000000..c44a76285
--- /dev/null
+++ b/drivers/mfd/rdc321x-southbridge.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * RDC321x MFD southbridge driver
+ *
+ * Copyright (C) 2007-2010 Florian Fainelli <florian@openwrt.org>
+ * Copyright (C) 2010 Bernhard Loos <bernhardloos@googlemail.com>
+ */
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/pci.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/rdc321x.h>
+
+static struct rdc321x_wdt_pdata rdc321x_wdt_pdata;
+
+static const struct resource rdc321x_wdt_resource[] = {
+	{
+		.name	= "wdt-reg",
+		.start	= RDC321X_WDT_CTRL,
+		.end	= RDC321X_WDT_CTRL + 0x3,
+		.flags	= IORESOURCE_IO,
+	}
+};
+
+static struct rdc321x_gpio_pdata rdc321x_gpio_pdata = {
+	.max_gpios	= RDC321X_NUM_GPIO,
+};
+
+static const struct resource rdc321x_gpio_resources[] = {
+	{
+		.name	= "gpio-reg1",
+		.start	= RDC321X_GPIO_CTRL_REG1,
+		.end	= RDC321X_GPIO_CTRL_REG1 + 0x7,
+		.flags	= IORESOURCE_IO,
+	}, {
+		.name	= "gpio-reg2",
+		.start	= RDC321X_GPIO_CTRL_REG2,
+		.end	= RDC321X_GPIO_CTRL_REG2 + 0x7,
+		.flags	= IORESOURCE_IO,
+	}
+};
+
+static const struct mfd_cell rdc321x_sb_cells[] = {
+	{
+		.name		= "rdc321x-wdt",
+		.resources	= rdc321x_wdt_resource,
+		.num_resources	= ARRAY_SIZE(rdc321x_wdt_resource),
+		.platform_data	= &rdc321x_wdt_pdata,
+		.pdata_size	= sizeof(rdc321x_wdt_pdata),
+	}, {
+		.name		= "rdc321x-gpio",
+		.resources	= rdc321x_gpio_resources,
+		.num_resources	= ARRAY_SIZE(rdc321x_gpio_resources),
+		.platform_data	= &rdc321x_gpio_pdata,
+		.pdata_size	= sizeof(rdc321x_gpio_pdata),
+	},
+};
+
+static int rdc321x_sb_probe(struct pci_dev *pdev,
+					const struct pci_device_id *ent)
+{
+	int err;
+
+	err = pci_enable_device(pdev);
+	if (err) {
+		dev_err(&pdev->dev, "failed to enable device\n");
+		return err;
+	}
+
+	rdc321x_gpio_pdata.sb_pdev = pdev;
+	rdc321x_wdt_pdata.sb_pdev = pdev;
+
+	return devm_mfd_add_devices(&pdev->dev, -1,
+				    rdc321x_sb_cells,
+				    ARRAY_SIZE(rdc321x_sb_cells),
+				    NULL, 0, NULL);
+}
+
+static const struct pci_device_id rdc321x_sb_table[] = {
+	{ PCI_DEVICE(PCI_VENDOR_ID_RDC, PCI_DEVICE_ID_RDC_R6030) },
+	{}
+};
+MODULE_DEVICE_TABLE(pci, rdc321x_sb_table);
+
+static struct pci_driver rdc321x_sb_driver = {
+	.name		= "RDC321x Southbridge",
+	.id_table	= rdc321x_sb_table,
+	.probe		= rdc321x_sb_probe,
+};
+
+module_pci_driver(rdc321x_sb_driver);
+
+MODULE_AUTHOR("Florian Fainelli <florian@openwrt.org>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("RDC R-321x MFD southbridge driver");