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, 68 insertions, 0 deletions

diff --git a/arch/arm/probes/decode-arm.h b/arch/arm/probes/decode-arm.h
new file mode 100644
index 000000000..48989c2e1
--- /dev/null
+++ b/arch/arm/probes/decode-arm.h
@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * arch/arm/probes/decode-arm.h
+ *
+ * Copyright 2013 Linaro Ltd.
+ * Written by: David A. Long
+ */
+
+#ifndef _ARM_KERNEL_PROBES_ARM_H
+#define  _ARM_KERNEL_PROBES_ARM_H
+
+#include "decode.h"
+
+enum probes_arm_action {
+	PROBES_PRELOAD_IMM,
+	PROBES_PRELOAD_REG,
+	PROBES_BRANCH_IMM,
+	PROBES_BRANCH_REG,
+	PROBES_MRS,
+	PROBES_CLZ,
+	PROBES_SATURATING_ARITHMETIC,
+	PROBES_MUL1,
+	PROBES_MUL2,
+	PROBES_SWP,
+	PROBES_LDRSTRD,
+	PROBES_LOAD,
+	PROBES_STORE,
+	PROBES_LOAD_EXTRA,
+	PROBES_STORE_EXTRA,
+	PROBES_MOV_IP_SP,
+	PROBES_DATA_PROCESSING_REG,
+	PROBES_DATA_PROCESSING_IMM,
+	PROBES_MOV_HALFWORD,
+	PROBES_SEV,
+	PROBES_WFE,
+	PROBES_SATURATE,
+	PROBES_REV,
+	PROBES_MMI,
+	PROBES_PACK,
+	PROBES_EXTEND,
+	PROBES_EXTEND_ADD,
+	PROBES_MUL_ADD_LONG,
+	PROBES_MUL_ADD,
+	PROBES_BITFIELD,
+	PROBES_BRANCH,
+	PROBES_LDMSTM,
+	NUM_PROBES_ARM_ACTIONS
+};
+
+void __kprobes simulate_bbl(probes_opcode_t opcode,
+	struct arch_probes_insn *asi, struct pt_regs *regs);
+void __kprobes simulate_blx1(probes_opcode_t opcode,
+	struct arch_probes_insn *asi, struct pt_regs *regs);
+void __kprobes simulate_blx2bx(probes_opcode_t opcode,
+	struct arch_probes_insn *asi, struct pt_regs *regs);
+void __kprobes simulate_mrs(probes_opcode_t opcode,
+	struct arch_probes_insn *asi, struct pt_regs *regs);
+void __kprobes simulate_mov_ipsp(probes_opcode_t opcode,
+	struct arch_probes_insn *asi, struct pt_regs *regs);
+
+extern const union decode_item probes_decode_arm_table[];
+
+enum probes_insn arm_probes_decode_insn(probes_opcode_t,
+		struct arch_probes_insn *, bool emulate,
+		const union decode_action *actions,
+		const struct decode_checker *checkers[]);
+
+#endif