A test case that would erroneously pass verification if
verifier.c:states_equal() maintains separate register ID mappings for
call frames.
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
tools/testing/selftests/bpf/verifier/calls.c | 82 ++++++++++++++++++++
1 file changed, 82 insertions(+)
diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c
index 3193915c5ee6..bcd15b26dcee 100644
--- a/tools/testing/selftests/bpf/verifier/calls.c
+++ b/tools/testing/selftests/bpf/verifier/calls.c
@@ -2305,3 +2305,85 @@
.errstr = "!read_ok",
.result = REJECT,
},
+/* Make sure that verifier.c:states_equal() considers IDs from all
+ * frames when building 'idmap' for check_ids().
+ */
+{
+ "calls: check_ids() across call boundary",
+ .insns = {
+ /* Function main() */
+ BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+ /* fp[-24] = map_lookup_elem(...) ; get a MAP_VALUE_PTR_OR_NULL with some ID */
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_LD_MAP_FD(BPF_REG_1,
+ 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_STX_MEM(BPF_DW, BPF_REG_FP, BPF_REG_0, -24),
+ /* fp[-32] = map_lookup_elem(...) ; get a MAP_VALUE_PTR_OR_NULL with some ID */
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_LD_MAP_FD(BPF_REG_1,
+ 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_STX_MEM(BPF_DW, BPF_REG_FP, BPF_REG_0, -32),
+ /* call foo(&fp[-24], &fp[-32]) ; both arguments have IDs in the current
+ * ; stack frame
+ */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_FP),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -24),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_FP),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -32),
+ BPF_CALL_REL(2),
+ /* exit 0 */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ /* Function foo()
+ *
+ * r9 = &frame[0].fp[-24] ; save arguments in the callee saved registers,
+ * r8 = &frame[0].fp[-32] ; arguments are pointers to pointers to map value
+ */
+ BPF_MOV64_REG(BPF_REG_9, BPF_REG_1),
+ BPF_MOV64_REG(BPF_REG_8, BPF_REG_2),
+ /* r7 = ktime_get_ns() */
+ BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns),
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
+ /* r6 = ktime_get_ns() */
+ BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns),
+ BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
+ /* if r6 > r7 goto +1 ; no new information about the state is derived from
+ * ; this check, thus produced verifier states differ
+ * ; only in 'insn_idx'
+ * r9 = r8
+ */
+ BPF_JMP_REG(BPF_JGT, BPF_REG_6, BPF_REG_7, 1),
+ BPF_MOV64_REG(BPF_REG_9, BPF_REG_8),
+ /* r9 = *r9 ; verifier get's to this point via two paths:
+ * ; (I) one including r9 = r8, verified first;
+ * ; (II) one excluding r9 = r8, verified next.
+ * ; After load of *r9 to r9 the frame[0].fp[-24].id == r9.id.
+ * ; Suppose that checkpoint is created here via path (I).
+ * ; When verifying via (II) the r9.id must be compared against
+ * ; frame[0].fp[-24].id, otherwise (I) and (II) would be
+ * ; incorrectly deemed equivalent.
+ * if r9 == 0 goto <exit>
+ */
+ BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_9, 0),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_9, 0, 1),
+ /* r8 = *r8 ; read map value via r8, this is not safe
+ * r0 = *r8 ; because r8 might be not equal to r9.
+ */
+ BPF_LDX_MEM(BPF_DW, BPF_REG_8, BPF_REG_8, 0),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_8, 0),
+ /* exit 0 */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .flags = BPF_F_TEST_STATE_FREQ,
+ .fixup_map_hash_8b = { 3, 9 },
+ .result = REJECT,
+ .errstr = "R8 invalid mem access 'map_value_or_null'",
+ .result_unpriv = REJECT,
+ .errstr_unpriv = "",
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+},
--
2.34.1
