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, 43 insertions, 0 deletions

diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
new file mode 100644
index 000000000..f4583dcaf
--- /dev/null
+++ b/fs/sysfs/sysfs.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * fs/sysfs/sysfs.h - sysfs internal header file
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ */
+
+#ifndef __SYSFS_INTERNAL_H
+#define __SYSFS_INTERNAL_H
+
+#include <linux/sysfs.h>
+
+/*
+ * mount.c
+ */
+extern struct kernfs_node *sysfs_root_kn;
+
+/*
+ * dir.c
+ */
+extern spinlock_t sysfs_symlink_target_lock;
+
+void sysfs_warn_dup(struct kernfs_node *parent, const char *name);
+
+/*
+ * file.c
+ */
+int sysfs_add_file_mode_ns(struct kernfs_node *parent,
+		const struct attribute *attr, umode_t amode, kuid_t uid,
+		kgid_t gid, const struct ns_common *ns);
+int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
+		const struct bin_attribute *battr, umode_t mode, size_t size,
+		kuid_t uid, kgid_t gid, const struct ns_common *ns);
+
+/*
+ * symlink.c
+ */
+int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
+			 const char *name);
+
+#endif	/* __SYSFS_INTERNAL_H */