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, 46 insertions, 0 deletions

diff --git a/sound/usb/helper.h b/sound/usb/helper.h
new file mode 100644
index 000000000..0372e050b
--- /dev/null
+++ b/sound/usb/helper.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __USBAUDIO_HELPER_H
+#define __USBAUDIO_HELPER_H
+
+unsigned int snd_usb_combine_bytes(unsigned char *bytes, int size);
+
+void *snd_usb_find_desc(void *descstart, int desclen, void *after, u8 dtype);
+void *snd_usb_find_csint_desc(void *descstart, int desclen, void *after, u8 dsubtype);
+
+int snd_usb_ctl_msg(struct usb_device *dev, unsigned int pipe,
+		    __u8 request, __u8 requesttype, __u16 value, __u16 index,
+		    void *data, __u16 size);
+
+unsigned char snd_usb_parse_datainterval(struct snd_usb_audio *chip,
+					 struct usb_host_interface *alts);
+
+struct usb_host_interface *
+snd_usb_get_host_interface(struct snd_usb_audio *chip, int ifnum, int altsetting);
+
+int snd_usb_add_ctrl_interface_link(struct snd_usb_audio *chip, int ifnum,
+		int ctrlif);
+
+struct usb_host_interface *snd_usb_find_ctrl_interface(struct snd_usb_audio *chip,
+								int ifnum);
+
+/*
+ * retrieve usb_interface descriptor from the host interface
+ * (conditional for compatibility with the older API)
+ */
+#define get_iface_desc(iface)	(&(iface)->desc)
+#define get_endpoint(alt,ep)	(&(alt)->endpoint[ep].desc)
+#define get_ep_desc(ep)		(&(ep)->desc)
+#define get_cfg_desc(cfg)	(&(cfg)->desc)
+
+#define snd_usb_get_speed(dev) ((dev)->speed)
+
+static inline int snd_usb_ctrl_intf(struct usb_host_interface *ctrl_intf)
+{
+	return get_iface_desc(ctrl_intf)->bInterfaceNumber;
+}
+
+/* in validate.c */
+bool snd_usb_validate_audio_desc(void *p, int protocol);
+bool snd_usb_validate_midi_desc(void *p);
+
+#endif /* __USBAUDIO_HELPER_H */