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, 116 insertions, 0 deletions

diff --git a/arch/mips/cobalt/setup.c b/arch/mips/cobalt/setup.c
new file mode 100644
index 000000000..9a266bf78
--- /dev/null
+++ b/arch/mips/cobalt/setup.c
@@ -0,0 +1,116 @@
+/*
+ * Setup pointers to hardware dependent routines.
+ *
+ * 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) 1996, 1997, 2004, 05 by Ralf Baechle (ralf@linux-mips.org)
+ * Copyright (C) 2001, 2002, 2003 by Liam Davies (ldavies@agile.tv)
+ *
+ */
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/memblock.h>
+#include <linux/pm.h>
+
+#include <asm/bootinfo.h>
+#include <asm/reboot.h>
+#include <asm/setup.h>
+#include <asm/gt64120.h>
+
+#include <cobalt.h>
+
+const char *get_system_type(void)
+{
+	switch (cobalt_board_id) {
+		case COBALT_BRD_ID_QUBE1:
+			return "Cobalt Qube";
+		case COBALT_BRD_ID_RAQ1:
+			return "Cobalt RaQ";
+		case COBALT_BRD_ID_QUBE2:
+			return "Cobalt Qube2";
+		case COBALT_BRD_ID_RAQ2:
+			return "Cobalt RaQ2";
+	}
+	return "MIPS Cobalt";
+}
+
+/*
+ * Cobalt doesn't have PS/2 keyboard/mouse interfaces,
+ * keyboard controller is never used.
+ * Also PCI-ISA bridge DMA controller is never used.
+ */
+static struct resource cobalt_reserved_resources[] = {
+	{	/* dma1 */
+		.start	= 0x00,
+		.end	= 0x1f,
+		.name	= "reserved",
+		.flags	= IORESOURCE_BUSY | IORESOURCE_IO,
+	},
+	{	/* keyboard */
+		.start	= 0x60,
+		.end	= 0x6f,
+		.name	= "reserved",
+		.flags	= IORESOURCE_BUSY | IORESOURCE_IO,
+	},
+	{	/* dma page reg */
+		.start	= 0x80,
+		.end	= 0x8f,
+		.name	= "reserved",
+		.flags	= IORESOURCE_BUSY | IORESOURCE_IO,
+	},
+	{	/* dma2 */
+		.start	= 0xc0,
+		.end	= 0xdf,
+		.name	= "reserved",
+		.flags	= IORESOURCE_BUSY | IORESOURCE_IO,
+	},
+};
+
+void __init plat_mem_setup(void)
+{
+	int i;
+
+	_machine_restart = cobalt_machine_restart;
+	_machine_halt = cobalt_machine_halt;
+	pm_power_off = cobalt_machine_halt;
+
+	set_io_port_base(CKSEG1ADDR(GT_DEF_PCI0_IO_BASE));
+
+	/* I/O port resource */
+	ioport_resource.end = 0x01ffffff;
+
+	/* These resources have been reserved by VIA SuperI/O chip. */
+	for (i = 0; i < ARRAY_SIZE(cobalt_reserved_resources); i++)
+		request_resource(&ioport_resource, cobalt_reserved_resources + i);
+}
+
+/*
+ * Prom init. We read our one and only communication with the firmware.
+ * Grab the amount of installed memory.
+ * Better boot loaders (CoLo) pass a command line too :-)
+ */
+
+void __init prom_init(void)
+{
+	unsigned long memsz;
+	int argc, i;
+	char **argv;
+
+	memsz = fw_arg0 & 0x7fff0000;
+	argc = fw_arg0 & 0x0000ffff;
+	argv = (char **)fw_arg1;
+
+	for (i = 1; i < argc; i++) {
+		strlcat(arcs_cmdline, argv[i], COMMAND_LINE_SIZE);
+		if (i < (argc - 1))
+			strlcat(arcs_cmdline, " ", COMMAND_LINE_SIZE);
+	}
+
+	memblock_add(0, memsz);
+
+	setup_8250_early_printk_port(CKSEG1ADDR(0x1c800000), 0, 0);
+}