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, 58 insertions, 0 deletions

diff --git a/drivers/misc/ibmasm/uart.c b/drivers/misc/ibmasm/uart.c
new file mode 100644
index 000000000..a5d4c8e01
--- /dev/null
+++ b/drivers/misc/ibmasm/uart.c
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/*
+ * IBM ASM Service Processor Device Driver
+ *
+ * Copyright (C) IBM Corporation, 2004
+ *
+ * Author: Max Asböck <amax@us.ibm.com>
+ */
+
+#include <linux/termios.h>
+#include <linux/tty.h>
+#include <linux/serial_core.h>
+#include <linux/serial_reg.h>
+#include <linux/serial_8250.h>
+#include "ibmasm.h"
+#include "lowlevel.h"
+
+
+void ibmasm_register_uart(struct service_processor *sp)
+{
+	struct uart_8250_port uart;
+	void __iomem *iomem_base;
+
+	iomem_base = sp->base_address + SCOUT_COM_B_BASE;
+
+	/* read the uart scratch register to determine if the UART
+	 * is dedicated to the service processor or if the OS can use it
+	 */
+	if (0 == readl(iomem_base + UART_SCR)) {
+		dev_info(sp->dev, "IBM SP UART not registered, owned by service processor\n");
+		sp->serial_line = -1;
+		return;
+	}
+
+	memset(&uart, 0, sizeof(uart));
+	uart.port.irq		= sp->irq;
+	uart.port.uartclk	= 3686400;
+	uart.port.flags		= UPF_SHARE_IRQ;
+	uart.port.iotype	= UPIO_MEM;
+	uart.port.membase	= iomem_base;
+
+	sp->serial_line = serial8250_register_8250_port(&uart);
+	if (sp->serial_line < 0) {
+		dev_err(sp->dev, "Failed to register serial port\n");
+		return;
+	}
+	enable_uart_interrupts(sp->base_address);
+}
+
+void ibmasm_unregister_uart(struct service_processor *sp)
+{
+	if (sp->serial_line < 0)
+		return;
+
+	disable_uart_interrupts(sp->base_address);
+	serial8250_unregister_port(sp->serial_line);
+}