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, 73 insertions, 0 deletions

diff --git a/arch/powerpc/boot/treeboot-iss4xx.c b/arch/powerpc/boot/treeboot-iss4xx.c
new file mode 100644
index 000000000..9ab556093
--- /dev/null
+++ b/arch/powerpc/boot/treeboot-iss4xx.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2010 Ben. Herrenschmidt, IBM Corporation.
+ *
+ * Based on earlier code:
+ *   Copyright (C) Paul Mackerras 1997.
+ *
+ *   Matt Porter <mporter@kernel.crashing.org>
+ *   Copyright 2002-2005 MontaVista Software Inc.
+ *
+ *   Eugene Surovegin <eugene.surovegin@zultys.com> or <ebs@ebshome.net>
+ *   Copyright (c) 2003, 2004 Zultys Technologies
+ *
+ *    Copyright 2007 David Gibson, IBM Corporation.
+ */
+#include <stdarg.h>
+#include <stddef.h>
+#include "types.h"
+#include "elf.h"
+#include "string.h"
+#include "stdio.h"
+#include "page.h"
+#include "ops.h"
+#include "reg.h"
+#include "io.h"
+#include "dcr.h"
+#include "4xx.h"
+#include "44x.h"
+#include "libfdt.h"
+
+BSS_STACK(4096);
+
+static u32 ibm4xx_memstart;
+
+static void iss_4xx_fixups(void)
+{
+	void *memory;
+	u32 reg[3];
+
+	memory = finddevice("/memory");
+	if (!memory)
+		fatal("Can't find memory node\n");
+	/* This assumes #address-cells = 2, #size-cells =1 and that */
+	getprop(memory, "reg", reg, sizeof(reg));
+	if (reg[2])
+		/* If the device tree specifies the memory range, use it */
+		ibm4xx_memstart = reg[1];
+	else
+		/* othersize, read it from the SDRAM controller */
+		ibm4xx_sdram_fixup_memsize();
+}
+
+static void *iss_4xx_vmlinux_alloc(unsigned long size)
+{
+	return (void *)ibm4xx_memstart;
+}
+
+#define SPRN_PIR	0x11E	/* Processor Identification Register */
+void platform_init(void)
+{
+	unsigned long end_of_ram = 0x08000000;
+	unsigned long avail_ram = end_of_ram - (unsigned long)_end;
+	u32 pir_reg;
+
+	simple_alloc_init(_end, avail_ram, 128, 64);
+	platform_ops.fixups = iss_4xx_fixups;
+	platform_ops.vmlinux_alloc = iss_4xx_vmlinux_alloc;
+	platform_ops.exit = ibm44x_dbcr_reset;
+	pir_reg = mfspr(SPRN_PIR);
+	fdt_set_boot_cpuid_phys(_dtb_start, pir_reg);
+	fdt_init(_dtb_start);
+	serial_console_init();
+}