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, 50 insertions, 0 deletions

diff --git a/include/net/tun_proto.h b/include/net/tun_proto.h
new file mode 100644
index 000000000..7b0de7852
--- /dev/null
+++ b/include/net/tun_proto.h
@@ -0,0 +1,50 @@
+#ifndef __NET_TUN_PROTO_H
+#define __NET_TUN_PROTO_H
+
+#include <linux/if_ether.h>
+#include <linux/types.h>
+
+/* One byte protocol values as defined by VXLAN-GPE and NSH. These will
+ * hopefully get a shared IANA registry.
+ */
+#define TUN_P_IPV4      0x01
+#define TUN_P_IPV6      0x02
+#define TUN_P_ETHERNET  0x03
+#define TUN_P_NSH       0x04
+#define TUN_P_MPLS_UC   0x05
+
+static inline __be16 tun_p_to_eth_p(u8 proto)
+{
+	switch (proto) {
+	case TUN_P_IPV4:
+		return htons(ETH_P_IP);
+	case TUN_P_IPV6:
+		return htons(ETH_P_IPV6);
+	case TUN_P_ETHERNET:
+		return htons(ETH_P_TEB);
+	case TUN_P_NSH:
+		return htons(ETH_P_NSH);
+	case TUN_P_MPLS_UC:
+		return htons(ETH_P_MPLS_UC);
+	}
+	return 0;
+}
+
+static inline u8 tun_p_from_eth_p(__be16 proto)
+{
+	switch (proto) {
+	case htons(ETH_P_IP):
+		return TUN_P_IPV4;
+	case htons(ETH_P_IPV6):
+		return TUN_P_IPV6;
+	case htons(ETH_P_TEB):
+		return TUN_P_ETHERNET;
+	case htons(ETH_P_NSH):
+		return TUN_P_NSH;
+	case htons(ETH_P_MPLS_UC):
+		return TUN_P_MPLS_UC;
+	}
+	return 0;
+}
+
+#endif