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, 63 insertions, 0 deletions

diff --git a/arch/powerpc/boot/epapr.c b/arch/powerpc/boot/epapr.c
new file mode 100644
index 000000000..7c5b26ade
--- /dev/null
+++ b/arch/powerpc/boot/epapr.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Bootwrapper for ePAPR compliant firmwares
+ *
+ * Copyright 2010 David Gibson <david@gibson.dropbear.id.au>, IBM Corporation.
+ *
+ * Based on earlier bootwrappers by:
+ * (c) Benjamin Herrenschmidt <benh@kernel.crashing.org>, IBM Corp,\
+ *   and
+ * Scott Wood <scottwood@freescale.com>
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ */
+
+#include "ops.h"
+#include "stdio.h"
+#include "io.h"
+#include <libfdt.h>
+
+BSS_STACK(4096);
+
+#define EPAPR_SMAGIC	0x65504150
+#define EPAPR_EMAGIC	0x45504150
+
+static unsigned epapr_magic;
+static unsigned long ima_size;
+static unsigned long fdt_addr;
+
+static void platform_fixups(void)
+{
+	if ((epapr_magic != EPAPR_EMAGIC)
+	    && (epapr_magic != EPAPR_SMAGIC))
+		fatal("r6 contained 0x%08x instead of ePAPR magic number\n",
+		      epapr_magic);
+
+	if (ima_size < (unsigned long)_end)
+		printf("WARNING: Image loaded outside IMA!"
+		       " (_end=%p, ima_size=0x%lx)\n", _end, ima_size);
+	if (ima_size < fdt_addr)
+		printf("WARNING: Device tree address is outside IMA!"
+		       "(fdt_addr=0x%lx, ima_size=0x%lx)\n", fdt_addr,
+		       ima_size);
+	if (ima_size < fdt_addr + fdt_totalsize((void *)fdt_addr))
+		printf("WARNING: Device tree extends outside IMA!"
+		       " (fdt_addr=0x%lx, size=0x%x, ima_size=0x%lx\n",
+		       fdt_addr, fdt_totalsize((void *)fdt_addr), ima_size);
+}
+
+void epapr_platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
+			 unsigned long r6, unsigned long r7)
+{
+	epapr_magic = r6;
+	ima_size = r7;
+	fdt_addr = r3;
+
+	/* FIXME: we should process reserve entries */
+
+	simple_alloc_init(_end, ima_size - (unsigned long)_end, 32, 64);
+
+	fdt_init((void *)fdt_addr);
+
+	serial_console_init();
+	platform_ops.fixups = platform_fixups;
+}