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, 77 insertions, 0 deletions

diff --git a/arch/mips/bcm63xx/dev-uart.c b/arch/mips/bcm63xx/dev-uart.c
new file mode 100644
index 000000000..5d6bf0445
--- /dev/null
+++ b/arch/mips/bcm63xx/dev-uart.c
@@ -0,0 +1,77 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2008 Maxime Bizon <mbizon@freebox.fr>
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <bcm63xx_cpu.h>
+#include <bcm63xx_dev_uart.h>
+
+static struct resource uart0_resources[] = {
+	{
+		/* start & end filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		/* start filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct resource uart1_resources[] = {
+	{
+		/* start & end filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		/* start filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct platform_device bcm63xx_uart_devices[] = {
+	{
+		.name		= "bcm63xx_uart",
+		.id		= 0,
+		.num_resources	= ARRAY_SIZE(uart0_resources),
+		.resource	= uart0_resources,
+	},
+
+	{
+		.name		= "bcm63xx_uart",
+		.id		= 1,
+		.num_resources	= ARRAY_SIZE(uart1_resources),
+		.resource	= uart1_resources,
+	}
+};
+
+int __init bcm63xx_uart_register(unsigned int id)
+{
+	if (id >= ARRAY_SIZE(bcm63xx_uart_devices))
+		return -ENODEV;
+
+	if (id == 1 && (!BCMCPU_IS_3368() && !BCMCPU_IS_6358() &&
+		!BCMCPU_IS_6368()))
+		return -ENODEV;
+
+	if (id == 0) {
+		uart0_resources[0].start = bcm63xx_regset_address(RSET_UART0);
+		uart0_resources[0].end = uart0_resources[0].start +
+			RSET_UART_SIZE - 1;
+		uart0_resources[1].start = bcm63xx_get_irq_number(IRQ_UART0);
+	}
+
+	if (id == 1) {
+		uart1_resources[0].start = bcm63xx_regset_address(RSET_UART1);
+		uart1_resources[0].end = uart1_resources[0].start +
+			RSET_UART_SIZE - 1;
+		uart1_resources[1].start = bcm63xx_get_irq_number(IRQ_UART1);
+	}
+
+	return platform_device_register(&bcm63xx_uart_devices[id]);
+}