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, 37 insertions, 0 deletions

diff --git a/sound/soc/codecs/cs4271-spi.c b/sound/soc/codecs/cs4271-spi.c
new file mode 100644
index 000000000..4feb80436
--- /dev/null
+++ b/sound/soc/codecs/cs4271-spi.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * CS4271 SPI audio driver
+ *
+ * Copyright (c) 2010 Alexander Sverdlin <subaparts@yandex.ru>
+ */
+
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/regmap.h>
+#include <sound/soc.h>
+#include "cs4271.h"
+
+static int cs4271_spi_probe(struct spi_device *spi)
+{
+	struct regmap_config config;
+
+	config = cs4271_regmap_config;
+	config.reg_bits = 16;
+	config.read_flag_mask = 0x21;
+	config.write_flag_mask = 0x20;
+
+	return cs4271_probe(&spi->dev, devm_regmap_init_spi(spi, &config));
+}
+
+static struct spi_driver cs4271_spi_driver = {
+	.driver = {
+		.name	= "cs4271",
+		.of_match_table = of_match_ptr(cs4271_dt_ids),
+	},
+	.probe		= cs4271_spi_probe,
+};
+module_spi_driver(cs4271_spi_driver);
+
+MODULE_DESCRIPTION("ASoC CS4271 SPI Driver");
+MODULE_AUTHOR("Alexander Sverdlin <subaparts@yandex.ru>");
+MODULE_LICENSE("GPL");