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, 35 insertions, 0 deletions

diff --git a/fs/btrfs/verity.h b/fs/btrfs/verity.h
new file mode 100644
index 000000000..d696659e4
--- /dev/null
+++ b/fs/btrfs/verity.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef BTRFS_VERITY_H
+#define BTRFS_VERITY_H
+
+struct inode;
+struct btrfs_inode;
+
+#ifdef CONFIG_FS_VERITY
+
+#include <linux/fsverity.h>
+
+extern const struct fsverity_operations btrfs_verityops;
+
+int btrfs_drop_verity_items(struct btrfs_inode *inode);
+int btrfs_get_verity_descriptor(struct inode *inode, void *buf, size_t buf_size);
+
+#else
+
+#include <linux/errno.h>
+
+static inline int btrfs_drop_verity_items(struct btrfs_inode *inode)
+{
+	return 0;
+}
+
+static inline int btrfs_get_verity_descriptor(struct inode *inode, void *buf,
+					      size_t buf_size)
+{
+	return -EPERM;
+}
+
+#endif
+
+#endif