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, 82 insertions, 0 deletions

diff --git a/include/sound/ac97/controller.h b/include/sound/ac97/controller.h
new file mode 100644
index 000000000..d5895ea39
--- /dev/null
+++ b/include/sound/ac97/controller.h
@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2016 Robert Jarzmik <robert.jarzmik@free.fr>
+ */
+
+#ifndef AC97_CONTROLLER_H
+#define AC97_CONTROLLER_H
+
+#include <linux/device.h>
+#include <linux/list.h>
+
+#define AC97_BUS_MAX_CODECS 4
+#define AC97_SLOTS_AVAILABLE_ALL 0xf
+
+struct ac97_controller_ops;
+
+/**
+ * struct ac97_controller - The AC97 controller of the AC-Link
+ * @ops:		the AC97 operations.
+ * @controllers:	linked list of all existing controllers.
+ * @adap:		the shell device ac97-%d, ie. ac97 adapter
+ * @nr:			the number of the shell device
+ * @slots_available:	the mask of accessible/scanable codecs.
+ * @parent:		the device providing the AC97 controller.
+ * @codecs:		the 4 possible AC97 codecs (NULL if none found).
+ * @codecs_pdata:	platform_data for each codec (NULL if no pdata).
+ *
+ * This structure is internal to AC97 bus, and should not be used by the
+ * controllers themselves, excepting for using @dev.
+ */
+struct ac97_controller {
+	const struct ac97_controller_ops *ops;
+	struct list_head controllers;
+	struct device adap;
+	int nr;
+	unsigned short slots_available;
+	struct device *parent;
+	struct ac97_codec_device *codecs[AC97_BUS_MAX_CODECS];
+	void *codecs_pdata[AC97_BUS_MAX_CODECS];
+};
+
+/**
+ * struct ac97_controller_ops - The AC97 operations
+ * @reset:	Cold reset of the AC97 AC-Link.
+ * @warm_reset:	Warm reset of the AC97 AC-Link.
+ * @read:	Read of a single AC97 register.
+ *		Returns the register value or a negative error code.
+ * @write:	Write of a single AC97 register.
+ *
+ * These are the basic operation an AC97 controller must provide for an AC97
+ * access functions. Amongst these, all but the last 2 are mandatory.
+ * The slot number is also known as the AC97 codec number, between 0 and 3.
+ */
+struct ac97_controller_ops {
+	void (*reset)(struct ac97_controller *adrv);
+	void (*warm_reset)(struct ac97_controller *adrv);
+	int (*write)(struct ac97_controller *adrv, int slot,
+		     unsigned short reg, unsigned short val);
+	int (*read)(struct ac97_controller *adrv, int slot, unsigned short reg);
+};
+
+#if IS_ENABLED(CONFIG_AC97_BUS_NEW)
+struct ac97_controller *snd_ac97_controller_register(
+	const struct ac97_controller_ops *ops, struct device *dev,
+	unsigned short slots_available);
+void snd_ac97_controller_unregister(struct ac97_controller *ac97_ctrl);
+#else
+static inline struct ac97_controller *
+snd_ac97_controller_register(const struct ac97_controller_ops *ops,
+			     struct device *dev,
+			     unsigned short slots_available)
+{
+	return ERR_PTR(-ENODEV);
+}
+
+static inline void
+snd_ac97_controller_unregister(struct ac97_controller *ac97_ctrl)
+{
+}
+#endif
+
+#endif