selftests/bpf: add a test for a pruning bug in the verifier

The test makes a read through a map value pointer, then considers pruning
 a branch where the register holds an adjusted map value pointer.  It
 should not prune, but currently it does.

Signed-off-by: Alexei Starovoitov <ast@fb.com>
[ecree@solarflare.com: added test-name and patch description]
Signed-off-by: Edward Cree <ecree@solarflare.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index c912734d23643e5c4a1f33c0ca9f28a397bda5c4..353d1701564178b10b004192cf7840765d25a742 100644 (file)
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -6503,6 +6503,34 @@ static struct bpf_test tests[] = {
                .result = REJECT,
                .prog_type = BPF_PROG_TYPE_LWT_IN,
        },
+       {
+               "varlen_map_value_access pruning",
+               .insns = {
+                       BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+                       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_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+                                    BPF_FUNC_map_lookup_elem),
+                       BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 8),
+                       BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, 0),
+                       BPF_MOV32_IMM(BPF_REG_2, MAX_ENTRIES),
+                       BPF_JMP_REG(BPF_JSGT, BPF_REG_2, BPF_REG_1, 1),
+                       BPF_MOV32_IMM(BPF_REG_1, 0),
+                       BPF_ALU32_IMM(BPF_LSH, BPF_REG_1, 2),
+                       BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1),
+                       BPF_JMP_IMM(BPF_JA, 0, 0, 0),
+                       BPF_ST_MEM(BPF_DW, BPF_REG_0, 0,
+                                  offsetof(struct test_val, foo)),
+                       BPF_EXIT_INSN(),
+               },
+               .fixup_map2 = { 3 },
+               .errstr_unpriv = "R0 leaks addr",
+               .errstr = "R0 unbounded memory access",
+               .result_unpriv = REJECT,
+               .result = REJECT,
+               .flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
+       },
 };
 
 static int probe_filter_length(const struct bpf_insn *fp)