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>

2 files changed, 38 insertions, 0 deletions

diff --git a/arch/arc/plat-sim/Makefile b/arch/arc/plat-sim/Makefile
new file mode 100644
index 000000000..ea9389bf8
--- /dev/null
+++ b/arch/arc/plat-sim/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Copyright (C) 2011-2012 Synopsys, Inc. (www.synopsys.com)
+#
+
+obj-y := platform.o
diff --git a/arch/arc/plat-sim/platform.c b/arch/arc/plat-sim/platform.c
new file mode 100644
index 000000000..2bde2a6e3
--- /dev/null
+++ b/arch/arc/plat-sim/platform.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ARC simulation Platform support code
+ *
+ * Copyright (C) 2012 Synopsys, Inc. (www.synopsys.com)
+ */
+
+#include <linux/init.h>
+#include <asm/mach_desc.h>
+
+/*----------------------- Machine Descriptions ------------------------------
+ *
+ * Machine description is simply a set of platform/board specific callbacks
+ * This is not directly related to DeviceTree based dynamic device creation,
+ * however as part of early device tree scan, we also select the right
+ * callback set, by matching the DT compatible name.
+ */
+
+static const char *simulation_compat[] __initconst = {
+#ifdef CONFIG_ISA_ARCOMPACT
+	"snps,nsim",
+	"snps,nsimosci",
+#else
+	"snps,nsimosci_hs",
+	"snps,zebu_hs",
+#endif
+	NULL,
+};
+
+MACHINE_START(SIMULATION, "simulation")
+	.dt_compat	= simulation_compat,
+MACHINE_END