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, 18 insertions, 0 deletions

diff --git a/drivers/net/arcnet/com9026.h b/drivers/net/arcnet/com9026.h
new file mode 100644
index 000000000..6adbc1871
--- /dev/null
+++ b/drivers/net/arcnet/com9026.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __COM9026_H
+#define __COM9026_H
+
+/* COM 9026 controller chip --> ARCnet register addresses */
+
+#define COM9026_REG_W_INTMASK	0	/* writable */
+#define COM9026_REG_R_STATUS	0	/* readable */
+#define COM9026_REG_W_COMMAND	1	/* writable, returns random vals on read (?) */
+#define COM9026_REG_RW_CONFIG	2	/* Configuration register */
+#define COM9026_REG_R_RESET	8	/* software reset (on read) */
+#define COM9026_REG_RW_MEMDATA	12	/* Data port for IO-mapped memory */
+#define COM9026_REG_W_ADDR_LO	14	/* Control registers for said */
+#define COM9026_REG_W_ADDR_HI	15
+
+#define COM9026_REG_R_STATION	1	/* Station ID */
+
+#endif