bpf: Add selftest cases for ctx_or_null argument type

Add various tests to make sure the verifier keeps catching them:

  # ./test_verifier
  [...]
  torvalds#230/p pass ctx or null check, 1: ctx OK
  torvalds#231/p pass ctx or null check, 2: null OK
  torvalds#232/p pass ctx or null check, 3: 1 OK
  torvalds#233/p pass ctx or null check, 4: ctx - const OK
  torvalds#234/p pass ctx or null check, 5: null (connect) OK
  torvalds#235/p pass ctx or null check, 6: null (bind) OK
  torvalds#236/p pass ctx or null check, 7: ctx (bind) OK
  torvalds#237/p pass ctx or null check, 8: null (bind) OK
  [...]
  Summary: 1595 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/c74758d07b1b678036465ef7f068a49e9efd3548.1585323121.git.daniel@iogearbox.net

Author: borkmann

tools/testing/selftests/bpf/verifier/ctx.c

@@ -91,3 +91,108 @@
 	.result = REJECT,
 	.errstr = "variable ctx access var_off=(0x0; 0x4)",
 },
+{
+	"pass ctx or null check, 1: ctx",
+	.insns = {
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_netns_cookie),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
+	.expected_attach_type = BPF_CGROUP_UDP6_SENDMSG,
+	.result = ACCEPT,
+},
+{
+	"pass ctx or null check, 2: null",
+	.insns = {
+		BPF_MOV64_IMM(BPF_REG_1, 0),
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_netns_cookie),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
+	.expected_attach_type = BPF_CGROUP_UDP6_SENDMSG,
+	.result = ACCEPT,
+},
+{
+	"pass ctx or null check, 3: 1",
+	.insns = {
+		BPF_MOV64_IMM(BPF_REG_1, 1),
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_netns_cookie),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
+	.expected_attach_type = BPF_CGROUP_UDP6_SENDMSG,
+	.result = REJECT,
+	.errstr = "R1 type=inv expected=ctx",
+},
+{
+	"pass ctx or null check, 4: ctx - const",
+	.insns = {
+		BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -612),
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_netns_cookie),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
+	.expected_attach_type = BPF_CGROUP_UDP6_SENDMSG,
+	.result = REJECT,
+	.errstr = "dereference of modified ctx ptr",
+},
+{
+	"pass ctx or null check, 5: null (connect)",
+	.insns = {
+		BPF_MOV64_IMM(BPF_REG_1, 0),
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_netns_cookie),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
+	.expected_attach_type = BPF_CGROUP_INET4_CONNECT,
+	.result = ACCEPT,
+},
+{
+	"pass ctx or null check, 6: null (bind)",
+	.insns = {
+		BPF_MOV64_IMM(BPF_REG_1, 0),
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_netns_cookie),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
+	.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+	.result = ACCEPT,
+},
+{
+	"pass ctx or null check, 7: ctx (bind)",
+	.insns = {
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_socket_cookie),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
+	.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+	.result = ACCEPT,
+},
+{
+	"pass ctx or null check, 8: null (bind)",
+	.insns = {
+		BPF_MOV64_IMM(BPF_REG_1, 0),
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+			     BPF_FUNC_get_socket_cookie),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_CGROUP_SOCK,
+	.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+	.result = REJECT,
+	.errstr = "R1 type=inv expected=ctx",
+},