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, 42 insertions, 0 deletions

diff --git a/init/do_mounts.h b/init/do_mounts.h
new file mode 100644
index 000000000..a386ee531
--- /dev/null
+++ b/init/do_mounts.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/kernel.h>
+#include <linux/blkdev.h>
+#include <linux/init.h>
+#include <linux/syscalls.h>
+#include <linux/unistd.h>
+#include <linux/slab.h>
+#include <linux/mount.h>
+#include <linux/major.h>
+#include <linux/root_dev.h>
+#include <linux/init_syscalls.h>
+#include <linux/task_work.h>
+#include <linux/file.h>
+
+void  mount_root_generic(char *name, char *pretty_name, int flags);
+void  mount_root(char *root_device_name);
+extern int root_mountflags;
+
+static inline __init int create_dev(char *name, dev_t dev)
+{
+	init_unlink(name);
+	return init_mknod(name, S_IFBLK | 0600, new_encode_dev(dev));
+}
+
+#ifdef CONFIG_BLK_DEV_RAM
+int __init rd_load_image(void);
+#else
+static inline int rd_load_image(void) { return 0; }
+#endif
+
+#ifdef CONFIG_BLK_DEV_INITRD
+void __init initrd_load(void);
+#else
+static inline void initrd_load(void) { }
+#endif
+
+/* Ensure that async file closing finished to prevent spurious errors. */
+static inline void init_flush_fput(void)
+{
+	flush_delayed_fput();
+	task_work_run();
+}