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, 120 insertions, 0 deletions

diff --git a/drivers/net/phy/amd.c b/drivers/net/phy/amd.c
new file mode 100644
index 000000000..75b5fe655
--- /dev/null
+++ b/drivers/net/phy/amd.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Driver for AMD am79c PHYs
+ *
+ * Author: Heiko Schocher <hs@denx.de>
+ *
+ * Copyright (c) 2011 DENX Software Engineering GmbH
+ */
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mii.h>
+#include <linux/phy.h>
+
+#define PHY_ID_AC101L		0x00225520
+#define PHY_ID_AM79C874		0x0022561b
+
+#define MII_AM79C_IR		17	/* Interrupt Status/Control Register */
+#define MII_AM79C_IR_EN_LINK	0x0400	/* IR enable Linkstate */
+#define MII_AM79C_IR_EN_ANEG	0x0100	/* IR enable Aneg Complete */
+#define MII_AM79C_IR_IMASK_INIT	(MII_AM79C_IR_EN_LINK | MII_AM79C_IR_EN_ANEG)
+
+#define MII_AM79C_IR_LINK_DOWN	BIT(2)
+#define MII_AM79C_IR_ANEG_DONE	BIT(0)
+#define MII_AM79C_IR_IMASK_STAT	(MII_AM79C_IR_LINK_DOWN | MII_AM79C_IR_ANEG_DONE)
+
+MODULE_DESCRIPTION("AMD PHY driver");
+MODULE_AUTHOR("Heiko Schocher <hs@denx.de>");
+MODULE_LICENSE("GPL");
+
+static int am79c_ack_interrupt(struct phy_device *phydev)
+{
+	int err;
+
+	err = phy_read(phydev, MII_BMSR);
+	if (err < 0)
+		return err;
+
+	err = phy_read(phydev, MII_AM79C_IR);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static int am79c_config_init(struct phy_device *phydev)
+{
+	return 0;
+}
+
+static int am79c_config_intr(struct phy_device *phydev)
+{
+	int err;
+
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		err = am79c_ack_interrupt(phydev);
+		if (err)
+			return err;
+
+		err = phy_write(phydev, MII_AM79C_IR, MII_AM79C_IR_IMASK_INIT);
+	} else {
+		err = phy_write(phydev, MII_AM79C_IR, 0);
+		if (err)
+			return err;
+
+		err = am79c_ack_interrupt(phydev);
+	}
+
+	return err;
+}
+
+static irqreturn_t am79c_handle_interrupt(struct phy_device *phydev)
+{
+	int irq_status;
+
+	irq_status = phy_read(phydev, MII_AM79C_IR);
+	if (irq_status < 0) {
+		phy_error(phydev);
+		return IRQ_NONE;
+	}
+
+	if (!(irq_status & MII_AM79C_IR_IMASK_STAT))
+		return IRQ_NONE;
+
+	phy_trigger_machine(phydev);
+
+	return IRQ_HANDLED;
+}
+
+static struct phy_driver am79c_drivers[] = {
+	{
+		.phy_id		= PHY_ID_AM79C874,
+		.name		= "AM79C874",
+		.phy_id_mask	= 0xfffffff0,
+		/* PHY_BASIC_FEATURES */
+		.config_init	= am79c_config_init,
+		.config_intr	= am79c_config_intr,
+		.handle_interrupt = am79c_handle_interrupt,
+	},
+	{
+		.phy_id		= PHY_ID_AC101L,
+		.name		= "AC101L",
+		.phy_id_mask	= 0xfffffff0,
+		/* PHY_BASIC_FEATURES */
+		.config_init	= am79c_config_init,
+		.config_intr	= am79c_config_intr,
+		.handle_interrupt = am79c_handle_interrupt,
+	},
+};
+
+module_phy_driver(am79c_drivers);
+
+static const struct mdio_device_id __maybe_unused amd_tbl[] = {
+	{ PHY_ID_AC101L, 0xfffffff0 },
+	{ PHY_ID_AM79C874, 0xfffffff0 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(mdio, amd_tbl);