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/include/net/nfc/llc.h b/include/net/nfc/llc.h
new file mode 100644
index 000000000..1f699cb17
--- /dev/null
+++ b/include/net/nfc/llc.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Link Layer Control manager public interface
+ *
+ * Copyright (C) 2012  Intel Corporation. All rights reserved.
+ */
+
+#ifndef __NFC_LLC_H_
+#define __NFC_LLC_H_
+
+#include <net/nfc/hci.h>
+#include <linux/skbuff.h>
+
+#define LLC_NOP_NAME "nop"
+#define LLC_SHDLC_NAME "shdlc"
+
+typedef void (*rcv_to_hci_t) (struct nfc_hci_dev *hdev, struct sk_buff *skb);
+typedef int (*xmit_to_drv_t) (struct nfc_hci_dev *hdev, struct sk_buff *skb);
+typedef void (*llc_failure_t) (struct nfc_hci_dev *hdev, int err);
+
+struct nfc_llc;
+
+struct nfc_llc *nfc_llc_allocate(const char *name, struct nfc_hci_dev *hdev,
+				 xmit_to_drv_t xmit_to_drv,
+				 rcv_to_hci_t rcv_to_hci, int tx_headroom,
+				 int tx_tailroom, llc_failure_t llc_failure);
+void nfc_llc_free(struct nfc_llc *llc);
+
+int nfc_llc_start(struct nfc_llc *llc);
+int nfc_llc_stop(struct nfc_llc *llc);
+void nfc_llc_rcv_from_drv(struct nfc_llc *llc, struct sk_buff *skb);
+int nfc_llc_xmit_from_hci(struct nfc_llc *llc, struct sk_buff *skb);
+
+int nfc_llc_init(void);
+void nfc_llc_exit(void);
+
+#endif /* __NFC_LLC_H_ */