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, 56 insertions, 0 deletions

diff --git a/fs/lockd/nlm.h b/fs/lockd/nlm.h
new file mode 100644
index 000000000..47be65d01
--- /dev/null
+++ b/fs/lockd/nlm.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Declarations for the Network Lock Manager protocol.
+ *
+ * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
+ */
+
+#ifndef _LOCKD_NLM_H
+#define _LOCKD_NLM_H
+
+
+/* Maximum file offset in file_lock.fl_end */
+# define NLM_OFFSET_MAX		((s32) 0x7fffffff)
+# define NLM4_OFFSET_MAX	((s64) ((~(u64)0) >> 1))
+
+/* Return states for NLM */
+enum {
+	NLM_LCK_GRANTED			= 0,
+	NLM_LCK_DENIED			= 1,
+	NLM_LCK_DENIED_NOLOCKS		= 2,
+	NLM_LCK_BLOCKED			= 3,
+	NLM_LCK_DENIED_GRACE_PERIOD	= 4,
+#ifdef CONFIG_LOCKD_V4
+	NLM_DEADLCK			= 5,
+	NLM_ROFS			= 6,
+	NLM_STALE_FH			= 7,
+	NLM_FBIG			= 8,
+	NLM_FAILED			= 9,
+#endif
+};
+
+#define NLM_PROGRAM		100021
+
+#define NLMPROC_NULL		0
+#define NLMPROC_TEST		1
+#define NLMPROC_LOCK		2
+#define NLMPROC_CANCEL		3
+#define NLMPROC_UNLOCK		4
+#define NLMPROC_GRANTED		5
+#define NLMPROC_TEST_MSG	6
+#define NLMPROC_LOCK_MSG	7
+#define NLMPROC_CANCEL_MSG	8
+#define NLMPROC_UNLOCK_MSG	9
+#define NLMPROC_GRANTED_MSG	10
+#define NLMPROC_TEST_RES	11
+#define NLMPROC_LOCK_RES	12
+#define NLMPROC_CANCEL_RES	13
+#define NLMPROC_UNLOCK_RES	14
+#define NLMPROC_GRANTED_RES	15
+#define NLMPROC_NSM_NOTIFY	16		/* statd callback */
+#define NLMPROC_SHARE		20
+#define NLMPROC_UNSHARE		21
+#define NLMPROC_NM_LOCK		22
+#define NLMPROC_FREE_ALL	23
+
+#endif /* _LOCKD_NLM_H */