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, 48 insertions, 0 deletions

diff --git a/arch/mips/cobalt/pci.c b/arch/mips/cobalt/pci.c
new file mode 100644
index 000000000..85ec9cc31
--- /dev/null
+++ b/arch/mips/cobalt/pci.c
@@ -0,0 +1,48 @@
+/*
+ * Register PCI controller.
+ *
+ * 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/pci.h>
+
+#include <asm/gt64120.h>
+
+extern struct pci_ops gt64xxx_pci0_ops;
+
+static struct resource cobalt_mem_resource = {
+	.start	= GT_DEF_PCI0_MEM0_BASE,
+	.end	= GT_DEF_PCI0_MEM0_BASE + GT_DEF_PCI0_MEM0_SIZE - 1,
+	.name	= "PCI memory",
+	.flags	= IORESOURCE_MEM,
+};
+
+static struct resource cobalt_io_resource = {
+	.start	= 0x1000,
+	.end	= 0xffffffUL,
+	.name	= "PCI I/O",
+	.flags	= IORESOURCE_IO,
+};
+
+static struct pci_controller cobalt_pci_controller = {
+	.pci_ops	= &gt64xxx_pci0_ops,
+	.mem_resource	= &cobalt_mem_resource,
+	.io_resource	= &cobalt_io_resource,
+	.io_offset	= 0 - GT_DEF_PCI0_IO_BASE,
+	.io_map_base	= CKSEG1ADDR(GT_DEF_PCI0_IO_BASE),
+};
+
+static int __init cobalt_pci_init(void)
+{
+	register_pci_controller(&cobalt_pci_controller);
+
+	return 0;
+}
+
+arch_initcall(cobalt_pci_init);