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, 24 insertions, 0 deletions

diff --git a/arch/arm/mach-versatile/realview.c b/arch/arm/mach-versatile/realview.c
new file mode 100644
index 000000000..36a6f6bc4
--- /dev/null
+++ b/arch/arm/mach-versatile/realview.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2014 Linaro Ltd.
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+#include <asm/mach/arch.h>
+
+static const char *const realview_dt_platform_compat[] __initconst = {
+	"arm,realview-eb",
+	"arm,realview-pb1176",
+	"arm,realview-pba8",
+	"arm,realview-pbx",
+	NULL,
+};
+
+DT_MACHINE_START(REALVIEW_DT, "ARM RealView Machine (Device Tree Support)")
+#ifdef CONFIG_ZONE_DMA
+	.dma_zone_size	= SZ_256M,
+#endif
+	.dt_compat	= realview_dt_platform_compat,
+	.l2c_aux_val = 0x0,
+	.l2c_aux_mask = ~0x0,
+MACHINE_END