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, 35 insertions, 0 deletions

diff --git a/arch/powerpc/boot/cuboot-warp.c b/arch/powerpc/boot/cuboot-warp.c
new file mode 100644
index 000000000..1ec0fa284
--- /dev/null
+++ b/arch/powerpc/boot/cuboot-warp.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2008 PIKA Technologies
+ *   Sean MacLennan <smaclennan@pikatech.com>
+ */
+
+#include "ops.h"
+#include "4xx.h"
+#include "cuboot.h"
+#include "stdio.h"
+
+#define TARGET_4xx
+#define TARGET_44x
+#include "ppcboot.h"
+
+static bd_t bd;
+
+static void warp_fixups(void)
+{
+	ibm440ep_fixup_clocks(66000000, 11059200, 50000000);
+	ibm4xx_sdram_fixup_memsize();
+	ibm4xx_fixup_ebc_ranges("/plb/opb/ebc");
+	dt_fixup_mac_address_by_alias("ethernet0", bd.bi_enetaddr);
+}
+
+void platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
+		   unsigned long r6, unsigned long r7)
+{
+	CUBOOT_INIT();
+
+	platform_ops.fixups = warp_fixups;
+	platform_ops.exit = ibm44x_dbcr_reset;
+	fdt_init(_dtb_start);
+	serial_console_init();
+}