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, 105 insertions, 0 deletions

diff --git a/fs/dlm/main.c b/fs/dlm/main.c
new file mode 100644
index 000000000..a44d16da7
--- /dev/null
+++ b/fs/dlm/main.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/******************************************************************************
+*******************************************************************************
+**
+**  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
+**  Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.
+**
+**
+*******************************************************************************
+******************************************************************************/
+
+#include <linux/module.h>
+
+#include "dlm_internal.h"
+#include "lockspace.h"
+#include "lock.h"
+#include "user.h"
+#include "memory.h"
+#include "config.h"
+#include "midcomms.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/dlm.h>
+
+struct workqueue_struct *dlm_wq;
+
+static int __init init_dlm(void)
+{
+	int error;
+
+	error = dlm_memory_init();
+	if (error)
+		goto out;
+
+	dlm_midcomms_init();
+
+	error = dlm_lockspace_init();
+	if (error)
+		goto out_mem;
+
+	error = dlm_config_init();
+	if (error)
+		goto out_lockspace;
+
+	dlm_register_debugfs();
+
+	error = dlm_user_init();
+	if (error)
+		goto out_debug;
+
+	error = dlm_plock_init();
+	if (error)
+		goto out_user;
+
+	dlm_wq = alloc_workqueue("dlm_wq", WQ_PERCPU, 0);
+	if (!dlm_wq) {
+		error = -ENOMEM;
+		goto out_plock;
+	}
+
+	printk("DLM installed\n");
+
+	return 0;
+
+ out_plock:
+	dlm_plock_exit();
+ out_user:
+	dlm_user_exit();
+ out_debug:
+	dlm_unregister_debugfs();
+	dlm_config_exit();
+ out_lockspace:
+	dlm_lockspace_exit();
+ out_mem:
+	dlm_midcomms_exit();
+	dlm_memory_exit();
+ out:
+	return error;
+}
+
+static void __exit exit_dlm(void)
+{
+	/* be sure every pending work e.g. freeing is done */
+	destroy_workqueue(dlm_wq);
+	dlm_plock_exit();
+	dlm_user_exit();
+	dlm_config_exit();
+	dlm_lockspace_exit();
+	dlm_midcomms_exit();
+	dlm_unregister_debugfs();
+	dlm_memory_exit();
+}
+
+module_init(init_dlm);
+module_exit(exit_dlm);
+
+MODULE_DESCRIPTION("Distributed Lock Manager");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
+
+EXPORT_SYMBOL_GPL(dlm_new_lockspace);
+EXPORT_SYMBOL_GPL(dlm_release_lockspace);
+EXPORT_SYMBOL_GPL(dlm_lock);
+EXPORT_SYMBOL_GPL(dlm_unlock);
+