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, 40 insertions, 0 deletions

diff --git a/fs/btrfs/acl.h b/fs/btrfs/acl.h
new file mode 100644
index 000000000..0458cd51e
--- /dev/null
+++ b/fs/btrfs/acl.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef BTRFS_ACL_H
+#define BTRFS_ACL_H
+
+#include <linux/types.h>
+
+struct posix_acl;
+struct inode;
+struct btrfs_trans_handle;
+
+#ifdef CONFIG_BTRFS_FS_POSIX_ACL
+
+struct mnt_idmap;
+struct dentry;
+
+struct posix_acl *btrfs_get_acl(struct inode *inode, int type, bool rcu);
+int btrfs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
+		  struct posix_acl *acl, int type);
+int __btrfs_set_acl(struct btrfs_trans_handle *trans, struct inode *inode,
+		    struct posix_acl *acl, int type);
+
+#else
+
+#include <linux/errno.h>
+
+struct btrfs_trans_handle;
+
+#define btrfs_get_acl NULL
+#define btrfs_set_acl NULL
+static inline int __btrfs_set_acl(struct btrfs_trans_handle *trans,
+				  struct inode *inode, struct posix_acl *acl,
+				  int type)
+{
+	return -EOPNOTSUPP;
+}
+
+#endif
+
+#endif