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, 45 insertions, 0 deletions

diff --git a/arch/powerpc/boot/bamboo.c b/arch/powerpc/boot/bamboo.c
new file mode 100644
index 000000000..dcdfa586a
--- /dev/null
+++ b/arch/powerpc/boot/bamboo.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright IBM Corporation, 2007
+ * Josh Boyer <jwboyer@linux.vnet.ibm.com>
+ *
+ * Based on ebony wrapper:
+ * Copyright 2007 David Gibson, IBM Corporation.
+ *
+ * Clocking code based on code by:
+ * Stefan Roese <sr@denx.de>
+ */
+#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 "dcr.h"
+#include "4xx.h"
+#include "44x.h"
+
+static u8 *bamboo_mac0, *bamboo_mac1;
+
+static void bamboo_fixups(void)
+{
+	unsigned long sysclk = 33333333;
+
+	ibm440ep_fixup_clocks(sysclk, 11059200, 25000000);
+	ibm4xx_sdram_fixup_memsize();
+	ibm4xx_quiesce_eth((u32 *)0xef600e00, (u32 *)0xef600f00);
+	dt_fixup_mac_address_by_alias("ethernet0", bamboo_mac0);
+	dt_fixup_mac_address_by_alias("ethernet1", bamboo_mac1);
+}
+
+void bamboo_init(void *mac0, void *mac1)
+{
+	platform_ops.fixups = bamboo_fixups;
+	platform_ops.exit = ibm44x_dbcr_reset;
+	bamboo_mac0 = mac0;
+	bamboo_mac1 = mac1;
+	fdt_init(_dtb_start);
+	serial_console_init();
+}