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, 22 insertions, 0 deletions

diff --git a/include/net/aligned_data.h b/include/net/aligned_data.h
new file mode 100644
index 000000000..e1a1c8aed
--- /dev/null
+++ b/include/net/aligned_data.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _NET_ALIGNED_DATA_H
+#define _NET_ALIGNED_DATA_H
+
+#include <linux/atomic.h>
+#include <linux/types.h>
+
+/* Structure holding cacheline aligned fields on SMP builds.
+ * Each field or group should have an ____cacheline_aligned_in_smp
+ * attribute to ensure no accidental false sharing can happen.
+ */
+struct net_aligned_data {
+	atomic64_t	net_cookie ____cacheline_aligned_in_smp;
+#if defined(CONFIG_INET)
+	atomic_long_t tcp_memory_allocated ____cacheline_aligned_in_smp;
+	atomic_long_t udp_memory_allocated ____cacheline_aligned_in_smp;
+#endif
+};
+
+extern struct net_aligned_data net_aligned_data;
+
+#endif /* _NET_ALIGNED_DATA_H */