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, 132 insertions, 0 deletions

diff --git a/include/net/garp.h b/include/net/garp.h
new file mode 100644
index 000000000..59a07b171
--- /dev/null
+++ b/include/net/garp.h
@@ -0,0 +1,132 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NET_GARP_H
+#define _NET_GARP_H
+
+#include <linux/if_ether.h>
+#include <linux/types.h>
+#include <net/stp.h>
+
+#define GARP_PROTOCOL_ID	0x1
+#define GARP_END_MARK		0x0
+
+struct garp_pdu_hdr {
+	__be16	protocol;
+};
+
+struct garp_msg_hdr {
+	u8	attrtype;
+};
+
+enum garp_attr_event {
+	GARP_LEAVE_ALL,
+	GARP_JOIN_EMPTY,
+	GARP_JOIN_IN,
+	GARP_LEAVE_EMPTY,
+	GARP_LEAVE_IN,
+	GARP_EMPTY,
+};
+
+struct garp_attr_hdr {
+	u8	len;
+	u8	event;
+	u8	data[];
+};
+
+struct garp_skb_cb {
+	u8	cur_type;
+};
+
+static inline struct garp_skb_cb *garp_cb(struct sk_buff *skb)
+{
+	BUILD_BUG_ON(sizeof(struct garp_skb_cb) >
+		     sizeof_field(struct sk_buff, cb));
+	return (struct garp_skb_cb *)skb->cb;
+}
+
+enum garp_applicant_state {
+	GARP_APPLICANT_INVALID,
+	GARP_APPLICANT_VA,
+	GARP_APPLICANT_AA,
+	GARP_APPLICANT_QA,
+	GARP_APPLICANT_LA,
+	GARP_APPLICANT_VP,
+	GARP_APPLICANT_AP,
+	GARP_APPLICANT_QP,
+	GARP_APPLICANT_VO,
+	GARP_APPLICANT_AO,
+	GARP_APPLICANT_QO,
+	__GARP_APPLICANT_MAX
+};
+#define GARP_APPLICANT_MAX	(__GARP_APPLICANT_MAX - 1)
+
+enum garp_event {
+	GARP_EVENT_REQ_JOIN,
+	GARP_EVENT_REQ_LEAVE,
+	GARP_EVENT_R_JOIN_IN,
+	GARP_EVENT_R_JOIN_EMPTY,
+	GARP_EVENT_R_EMPTY,
+	GARP_EVENT_R_LEAVE_IN,
+	GARP_EVENT_R_LEAVE_EMPTY,
+	GARP_EVENT_TRANSMIT_PDU,
+	__GARP_EVENT_MAX
+};
+#define GARP_EVENT_MAX		(__GARP_EVENT_MAX - 1)
+
+enum garp_action {
+	GARP_ACTION_NONE,
+	GARP_ACTION_S_JOIN_IN,
+	GARP_ACTION_S_LEAVE_EMPTY,
+};
+
+struct garp_attr {
+	struct rb_node			node;
+	enum garp_applicant_state	state;
+	u8				type;
+	u8				dlen;
+	unsigned char			data[];
+};
+
+enum garp_applications {
+	GARP_APPLICATION_GVRP,
+	__GARP_APPLICATION_MAX
+};
+#define GARP_APPLICATION_MAX	(__GARP_APPLICATION_MAX - 1)
+
+struct garp_application {
+	enum garp_applications	type;
+	unsigned int		maxattr;
+	struct stp_proto	proto;
+};
+
+struct garp_applicant {
+	struct garp_application	*app;
+	struct net_device	*dev;
+	struct timer_list	join_timer;
+
+	spinlock_t		lock;
+	struct sk_buff_head	queue;
+	struct sk_buff		*pdu;
+	struct rb_root		gid;
+	struct rcu_head		rcu;
+};
+
+struct garp_port {
+	struct garp_applicant __rcu	*applicants[GARP_APPLICATION_MAX + 1];
+	struct rcu_head			rcu;
+};
+
+int garp_register_application(struct garp_application *app);
+void garp_unregister_application(struct garp_application *app);
+
+int garp_init_applicant(struct net_device *dev, struct garp_application *app);
+void garp_uninit_applicant(struct net_device *dev,
+			   struct garp_application *app);
+
+int garp_request_join(const struct net_device *dev,
+		      const struct garp_application *app, const void *data,
+		      u8 len, u8 type);
+void garp_request_leave(const struct net_device *dev,
+			const struct garp_application *app,
+			const void *data, u8 len, u8 type);
+
+#endif /* _NET_GARP_H */