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/security/landlock/limits.h b/security/landlock/limits.h
new file mode 100644
index 000000000..08d5f2f6d
--- /dev/null
+++ b/security/landlock/limits.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Landlock - Limits for different components
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018-2020 ANSSI
+ * Copyright © 2021-2025 Microsoft Corporation
+ */
+
+#ifndef _SECURITY_LANDLOCK_LIMITS_H
+#define _SECURITY_LANDLOCK_LIMITS_H
+
+#include <linux/bitops.h>
+#include <linux/limits.h>
+#include <uapi/linux/landlock.h>
+
+/* clang-format off */
+
+#define LANDLOCK_MAX_NUM_LAYERS		16
+#define LANDLOCK_MAX_NUM_RULES		U32_MAX
+
+#define LANDLOCK_LAST_ACCESS_FS		LANDLOCK_ACCESS_FS_RESOLVE_UNIX
+#define LANDLOCK_MASK_ACCESS_FS		((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
+#define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
+
+#define LANDLOCK_LAST_ACCESS_NET	LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP
+#define LANDLOCK_MASK_ACCESS_NET	((LANDLOCK_LAST_ACCESS_NET << 1) - 1)
+#define LANDLOCK_NUM_ACCESS_NET		__const_hweight64(LANDLOCK_MASK_ACCESS_NET)
+
+#define LANDLOCK_LAST_SCOPE		LANDLOCK_SCOPE_SIGNAL
+#define LANDLOCK_MASK_SCOPE		((LANDLOCK_LAST_SCOPE << 1) - 1)
+#define LANDLOCK_NUM_SCOPE		__const_hweight64(LANDLOCK_MASK_SCOPE)
+
+#define LANDLOCK_NUM_ACCESS_MAX \
+	MAX(MAX(LANDLOCK_NUM_ACCESS_FS, LANDLOCK_NUM_ACCESS_NET), LANDLOCK_NUM_SCOPE)
+
+#define LANDLOCK_LAST_RESTRICT_SELF	LANDLOCK_RESTRICT_SELF_TSYNC
+#define LANDLOCK_MASK_RESTRICT_SELF	((LANDLOCK_LAST_RESTRICT_SELF << 1) - 1)
+
+/* clang-format on */
+
+#endif /* _SECURITY_LANDLOCK_LIMITS_H */