[PATCH bpf-next 2/2] bpf: add tests for direct packet access from CGROUP_SKB

[Song Liu]

Tests are added to make sure CGROUP_SKB can directly access len, data,
and data_end in __sk_buff, but not other fields.

Signed-off-by: Song Liu <songliubrav...@fb.com>
---
 tools/testing/selftests/bpf/test_verifier.c | 30 +++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_verifier.c 
b/tools/testing/selftests/bpf/test_verifier.c
index cf4cd32b6772..aaf2ceba83dd 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -4862,6 +4862,36 @@ static struct bpf_test tests[] = {
                .result = REJECT,
                .flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
        },
+       {
+               "direct packet read for CGROUP_SKB",
+               .insns = {
+                       BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1,
+                                   offsetof(struct __sk_buff, data)),
+                       BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1,
+                                   offsetof(struct __sk_buff, data_end)),
+                       BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_1,
+                                   offsetof(struct __sk_buff, len)),
+                       BPF_MOV64_REG(BPF_REG_0, BPF_REG_2),
+                       BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 8),
+                       BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1),
+                       BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_2, 0),
+                       BPF_MOV64_IMM(BPF_REG_0, 0),
+                       BPF_EXIT_INSN(),
+               },
+               .result = ACCEPT,
+               .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+       },
+       {
+               "invalid access of tc_classid for CGROUP_SKB",
+               .insns = {
+                       BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+                                   offsetof(struct __sk_buff, tc_classid)),
+                       BPF_EXIT_INSN(),
+               },
+               .result = REJECT,
+               .errstr = "invalid bpf_context access",
+               .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+       },
        {
                "valid cgroup storage access",
                .insns = {
-- 
2.17.1