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, 95 insertions, 0 deletions

diff --git a/arch/arm/probes/decode-thumb.h b/arch/arm/probes/decode-thumb.h
new file mode 100644
index 000000000..84b445b8a
--- /dev/null
+++ b/arch/arm/probes/decode-thumb.h
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * arch/arm/probes/decode-thumb.h
+ *
+ * Copyright 2013 Linaro Ltd.
+ * Written by: David A. Long
+ */
+
+#ifndef _ARM_KERNEL_PROBES_THUMB_H
+#define  _ARM_KERNEL_PROBES_THUMB_H
+
+#include "decode.h"
+
+/*
+ * True if current instruction is in an IT block.
+ */
+#define in_it_block(cpsr)	((cpsr & 0x06000c00) != 0x00000000)
+
+/*
+ * Return the condition code to check for the currently executing instruction.
+ * This is in ITSTATE<7:4> which is in CPSR<15:12> but is only valid if
+ * in_it_block returns true.
+ */
+#define current_cond(cpsr)	((cpsr >> 12) & 0xf)
+
+enum probes_t32_action {
+	PROBES_T32_EMULATE_NONE,
+	PROBES_T32_SIMULATE_NOP,
+	PROBES_T32_LDMSTM,
+	PROBES_T32_LDRDSTRD,
+	PROBES_T32_TABLE_BRANCH,
+	PROBES_T32_TST,
+	PROBES_T32_CMP,
+	PROBES_T32_MOV,
+	PROBES_T32_ADDSUB,
+	PROBES_T32_LOGICAL,
+	PROBES_T32_ADDWSUBW_PC,
+	PROBES_T32_ADDWSUBW,
+	PROBES_T32_MOVW,
+	PROBES_T32_SAT,
+	PROBES_T32_BITFIELD,
+	PROBES_T32_SEV,
+	PROBES_T32_WFE,
+	PROBES_T32_MRS,
+	PROBES_T32_BRANCH_COND,
+	PROBES_T32_BRANCH,
+	PROBES_T32_PLDI,
+	PROBES_T32_LDR_LIT,
+	PROBES_T32_LDRSTR,
+	PROBES_T32_SIGN_EXTEND,
+	PROBES_T32_MEDIA,
+	PROBES_T32_REVERSE,
+	PROBES_T32_MUL_ADD,
+	PROBES_T32_MUL_ADD2,
+	PROBES_T32_MUL_ADD_LONG,
+	NUM_PROBES_T32_ACTIONS
+};
+
+enum probes_t16_action {
+	PROBES_T16_ADD_SP,
+	PROBES_T16_CBZ,
+	PROBES_T16_SIGN_EXTEND,
+	PROBES_T16_PUSH,
+	PROBES_T16_POP,
+	PROBES_T16_SEV,
+	PROBES_T16_WFE,
+	PROBES_T16_IT,
+	PROBES_T16_CMP,
+	PROBES_T16_ADDSUB,
+	PROBES_T16_LOGICAL,
+	PROBES_T16_BLX,
+	PROBES_T16_HIREGOPS,
+	PROBES_T16_LDR_LIT,
+	PROBES_T16_LDRHSTRH,
+	PROBES_T16_LDRSTR,
+	PROBES_T16_ADR,
+	PROBES_T16_LDMSTM,
+	PROBES_T16_BRANCH_COND,
+	PROBES_T16_BRANCH,
+	NUM_PROBES_T16_ACTIONS
+};
+
+extern const union decode_item probes_decode_thumb32_table[];
+extern const union decode_item probes_decode_thumb16_table[];
+
+enum probes_insn __kprobes
+thumb16_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
+		bool emulate, const union decode_action *actions,
+		const struct decode_checker *checkers[]);
+enum probes_insn __kprobes
+thumb32_probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
+		bool emulate, const union decode_action *actions,
+		const struct decode_checker *checkers[]);
+
+#endif