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, 37 insertions, 0 deletions

diff --git a/fs/dlm/lockspace.h b/fs/dlm/lockspace.h
new file mode 100644
index 000000000..47ebd4411
--- /dev/null
+++ b/fs/dlm/lockspace.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/******************************************************************************
+*******************************************************************************
+**
+**  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
+**  Copyright (C) 2004-2005 Red Hat, Inc.  All rights reserved.
+**
+**
+*******************************************************************************
+******************************************************************************/
+
+#ifndef __LOCKSPACE_DOT_H__
+#define __LOCKSPACE_DOT_H__
+
+/* DLM_LSFL_FS
+ *   The lockspace user is in the kernel (i.e. filesystem).  Enables
+ *   direct bast/cast callbacks.
+ *
+ * internal lockspace flag - will be removed in future
+ */
+#define DLM_LSFL_FS	0x00000004
+
+int dlm_lockspace_init(void);
+void dlm_lockspace_exit(void);
+struct dlm_ls *dlm_find_lockspace_global(uint32_t id);
+struct dlm_ls *dlm_find_lockspace_local(void *id);
+struct dlm_ls *dlm_find_lockspace_device(int minor);
+void dlm_put_lockspace(struct dlm_ls *ls);
+void dlm_stop_lockspaces(void);
+int dlm_new_user_lockspace(const char *name, const char *cluster,
+			   uint32_t flags, int lvblen,
+			   const struct dlm_lockspace_ops *ops,
+			   void *ops_arg, int *ops_result,
+			   dlm_lockspace_t **lockspace);
+
+#endif				/* __LOCKSPACE_DOT_H__ */
+