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, 54 insertions, 0 deletions

diff --git a/arch/powerpc/boot/fsl-soc.c b/arch/powerpc/boot/fsl-soc.c
new file mode 100644
index 000000000..01bad8ea6
--- /dev/null
+++ b/arch/powerpc/boot/fsl-soc.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Freescale SOC support functions
+ *
+ * Author: Scott Wood <scottwood@freescale.com>
+ *
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ */
+
+#include "ops.h"
+#include "types.h"
+#include "fsl-soc.h"
+#include "stdio.h"
+
+static u32 prop_buf[MAX_PROP_LEN / 4];
+
+u32 *fsl_get_immr(void)
+{
+	void *soc;
+	unsigned long ret = 0;
+
+	soc = find_node_by_devtype(NULL, "soc");
+	if (soc) {
+		int size;
+		u32 naddr;
+
+		size = getprop(soc, "#address-cells", prop_buf, MAX_PROP_LEN);
+		if (size == 4)
+			naddr = prop_buf[0];
+		else
+			naddr = 2;
+
+		if (naddr != 1 && naddr != 2)
+			goto err;
+
+		size = getprop(soc, "ranges", prop_buf, MAX_PROP_LEN);
+
+		if (size < 12)
+			goto err;
+		if (prop_buf[0] != 0)
+			goto err;
+		if (naddr == 2 && prop_buf[1] != 0)
+			goto err;
+
+		if (!dt_xlate_addr(soc, prop_buf + naddr, 8, &ret))
+			ret = 0;
+	}
+
+err:
+	if (!ret)
+		printf("fsl_get_immr: Failed to find immr base\r\n");
+
+	return (u32 *)ret;
+}