selftests/bpf: Check map in map pruning

Ensure that two registers with a map_value loaded from a nested map are considered equivalent for the purpose of state pruning and don't cause the verifier to revisit a pruning point. This uses a rather crude match on the number of insns visited by the verifier, which might change in the future. I've therefore tried to keep the code as "unpruneable" as possible by having the code paths only converge on the second to last instruction. Should you require to adjust the test in the future, reducing the number of processed instructions should always be safe. Increasing them could cause another regression, so proceed with caution. Suggested-by: Alexei Starovoitov <[email protected]> Signed-off-by: Lorenz Bauer <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]> Link: https://lore.kernel.org/bpf/CACAyw99hVEJFoiBH_ZGyy=+oO-jyydoz6v1DeKPKs2HVsUH28w@mail.gmail.com Link: https://lore.kernel.org/bpf/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>
ambv · Nov 13, 2021 · 6af2e12 · 6af2e12
1 parent 34d11a4
commit 6af2e12
Showing 1 changed file with 34 additions and 0 deletions.
diff --git a/tools/testing/selftests/bpf/verifier/map_in_map.c b/tools/testing/selftests/bpf/verifier/map_in_map.c
@@ -18,6 +18,40 @@
 	.fixup_map_in_map = { 3 },
 	.result = ACCEPT,
 },
+{
+	"map in map state pruning",
+	.insns = {
+	BPF_ST_MEM(0, BPF_REG_10, -4, 0),
+	BPF_MOV64_REG(BPF_REG_6, BPF_REG_10),
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_6, -4),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_6),
+	BPF_LD_MAP_FD(BPF_REG_1, 0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+	BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
+	BPF_EXIT_INSN(),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_6),
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+	BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 11),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_6),
+	BPF_LD_MAP_FD(BPF_REG_1, 0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+	BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
+	BPF_EXIT_INSN(),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_6),
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+	BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
+	BPF_EXIT_INSN(),
+	BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_0, 0),
+	BPF_EXIT_INSN(),
+	},
+	.fixup_map_in_map = { 4, 14 },
+	.flags = BPF_F_TEST_STATE_FREQ,
+	.result = VERBOSE_ACCEPT,
+	.errstr = "processed 25 insns",
+	.prog_type = BPF_PROG_TYPE_XDP,
+},
 {
 	"invalid inner map pointer",
 	.insns = {