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, 93 insertions, 0 deletions

diff --git a/arch/mips/bcm47xx/serial.c b/arch/mips/bcm47xx/serial.c
new file mode 100644
index 000000000..e3c9872a4
--- /dev/null
+++ b/arch/mips/bcm47xx/serial.c
@@ -0,0 +1,93 @@
+/*
+ * 8250 UART probe driver for the BCM47XX platforms
+ * Author: Aurelien Jarno
+ *
+ * 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) 2007 Aurelien Jarno <aurelien@aurel32.net>
+ */
+
+#include <linux/init.h>
+#include <linux/serial.h>
+#include <linux/serial_8250.h>
+#include <linux/ssb/ssb.h>
+#include <bcm47xx.h>
+
+static struct plat_serial8250_port uart8250_data[5];
+
+static struct platform_device uart8250_device = {
+	.name			= "serial8250",
+	.id			= PLAT8250_DEV_PLATFORM,
+	.dev			= {
+		.platform_data	= uart8250_data,
+	},
+};
+
+#ifdef CONFIG_BCM47XX_SSB
+static int __init uart8250_init_ssb(void)
+{
+	int i;
+	struct ssb_mipscore *mcore = &(bcm47xx_bus.ssb.mipscore);
+
+	memset(&uart8250_data, 0,  sizeof(uart8250_data));
+
+	for (i = 0; i < mcore->nr_serial_ports &&
+		    i < ARRAY_SIZE(uart8250_data) - 1; i++) {
+		struct plat_serial8250_port *p = &(uart8250_data[i]);
+		struct ssb_serial_port *ssb_port = &(mcore->serial_ports[i]);
+
+		p->mapbase = (unsigned int)ssb_port->regs;
+		p->membase = (void *)ssb_port->regs;
+		p->irq = ssb_port->irq + 2;
+		p->uartclk = ssb_port->baud_base;
+		p->regshift = ssb_port->reg_shift;
+		p->iotype = UPIO_MEM;
+		p->flags = UPF_BOOT_AUTOCONF | UPF_SHARE_IRQ;
+	}
+	return platform_device_register(&uart8250_device);
+}
+#endif
+
+#ifdef CONFIG_BCM47XX_BCMA
+static int __init uart8250_init_bcma(void)
+{
+	int i;
+	struct bcma_drv_cc *cc = &(bcm47xx_bus.bcma.bus.drv_cc);
+
+	memset(&uart8250_data, 0,  sizeof(uart8250_data));
+
+	for (i = 0; i < cc->nr_serial_ports &&
+		    i < ARRAY_SIZE(uart8250_data) - 1; i++) {
+		struct plat_serial8250_port *p = &(uart8250_data[i]);
+		struct bcma_serial_port *bcma_port;
+		bcma_port = &(cc->serial_ports[i]);
+
+		p->mapbase = (unsigned int)bcma_port->regs;
+		p->membase = (void *)bcma_port->regs;
+		p->irq = bcma_port->irq;
+		p->uartclk = bcma_port->baud_base;
+		p->regshift = bcma_port->reg_shift;
+		p->iotype = UPIO_MEM;
+		p->flags = UPF_BOOT_AUTOCONF | UPF_SHARE_IRQ;
+	}
+	return platform_device_register(&uart8250_device);
+}
+#endif
+
+static int __init uart8250_init(void)
+{
+	switch (bcm47xx_bus_type) {
+#ifdef CONFIG_BCM47XX_SSB
+	case BCM47XX_BUS_TYPE_SSB:
+		return uart8250_init_ssb();
+#endif
+#ifdef CONFIG_BCM47XX_BCMA
+	case BCM47XX_BUS_TYPE_BCMA:
+		return uart8250_init_bcma();
+#endif
+	}
+	return -EINVAL;
+}
+device_initcall(uart8250_init);