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, 124 insertions, 0 deletions

diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
new file mode 100644
index 000000000..4c5199b20
--- /dev/null
+++ b/include/crypto/public_key.h
@@ -0,0 +1,124 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Asymmetric public-key algorithm definitions
+ *
+ * See Documentation/crypto/asymmetric-keys.rst
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _LINUX_PUBLIC_KEY_H
+#define _LINUX_PUBLIC_KEY_H
+
+#include <linux/errno.h>
+#include <linux/keyctl.h>
+#include <linux/oid_registry.h>
+
+/*
+ * Cryptographic data for the public-key subtype of the asymmetric key type.
+ *
+ * Note that this may include private part of the key as well as the public
+ * part.
+ */
+struct public_key {
+	void *key;
+	u32 keylen;
+	enum OID algo;
+	void *params;
+	u32 paramlen;
+	bool key_is_private;
+	const char *id_type;
+	const char *pkey_algo;
+	unsigned long key_eflags;	/* key extension flags */
+#define KEY_EFLAG_CA		0	/* set if the CA basic constraints is set */
+#define KEY_EFLAG_DIGITALSIG	1	/* set if the digitalSignature usage is set */
+#define KEY_EFLAG_KEYCERTSIGN	2	/* set if the keyCertSign usage is set */
+};
+
+extern void public_key_free(struct public_key *key);
+
+/*
+ * Public key cryptography signature data
+ */
+struct public_key_signature {
+	struct asymmetric_key_id *auth_ids[3];
+	u8 *s;			/* Signature */
+	u8 *m;			/* Message data to pass to verifier */
+	u32 s_size;		/* Number of bytes in signature */
+	u32 m_size;		/* Number of bytes in ->m */
+	bool m_free;		/* T if ->m needs freeing */
+	bool algo_takes_data;	/* T if public key algo operates on data, not a hash */
+	const char *pkey_algo;
+	const char *hash_algo;
+	const char *encoding;
+};
+
+extern void public_key_signature_free(struct public_key_signature *sig);
+
+extern struct asymmetric_key_subtype public_key_subtype;
+
+struct key;
+struct key_type;
+union key_payload;
+
+extern int restrict_link_by_signature(struct key *dest_keyring,
+				      const struct key_type *type,
+				      const union key_payload *payload,
+				      struct key *trust_keyring);
+
+extern int restrict_link_by_key_or_keyring(struct key *dest_keyring,
+					   const struct key_type *type,
+					   const union key_payload *payload,
+					   struct key *trusted);
+
+extern int restrict_link_by_key_or_keyring_chain(struct key *trust_keyring,
+						 const struct key_type *type,
+						 const union key_payload *payload,
+						 struct key *trusted);
+
+#if IS_REACHABLE(CONFIG_ASYMMETRIC_KEY_TYPE)
+extern int restrict_link_by_ca(struct key *dest_keyring,
+			       const struct key_type *type,
+			       const union key_payload *payload,
+			       struct key *trust_keyring);
+int restrict_link_by_digsig(struct key *dest_keyring,
+			    const struct key_type *type,
+			    const union key_payload *payload,
+			    struct key *trust_keyring);
+#else
+static inline int restrict_link_by_ca(struct key *dest_keyring,
+				      const struct key_type *type,
+				      const union key_payload *payload,
+				      struct key *trust_keyring)
+{
+	return 0;
+}
+
+static inline int restrict_link_by_digsig(struct key *dest_keyring,
+					  const struct key_type *type,
+					  const union key_payload *payload,
+					  struct key *trust_keyring)
+{
+	return 0;
+}
+#endif
+
+extern int query_asymmetric_key(const struct kernel_pkey_params *,
+				struct kernel_pkey_query *);
+
+extern int verify_signature(const struct key *,
+			    const struct public_key_signature *);
+
+#if IS_REACHABLE(CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE)
+int public_key_verify_signature(const struct public_key *pkey,
+				const struct public_key_signature *sig);
+#else
+static inline
+int public_key_verify_signature(const struct public_key *pkey,
+				const struct public_key_signature *sig)
+{
+	return -EINVAL;
+}
+#endif
+
+#endif /* _LINUX_PUBLIC_KEY_H */