selftests/bpf: test references to sock_common

Make sure that returning a struct sock_common * reference invokes
the reference tracking machinery in the verifier.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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

@@ -9,6 +9,17 @@
 	.errstr = "Unreleased reference",
 	.result = REJECT,
 },
+{
+	"reference tracking: leak potential reference to sock_common",
+	.insns = {
+	BPF_SK_LOOKUP(skc_lookup_tcp),
+	BPF_MOV64_REG(BPF_REG_6, BPF_REG_0), /* leak reference */
+	BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+	.errstr = "Unreleased reference",
+	.result = REJECT,
+},
 {
 	"reference tracking: leak potential reference on stack",
 	.insns = {
@@ -49,6 +60,17 @@
 	.errstr = "Unreleased reference",
 	.result = REJECT,
 },
+{
+	"reference tracking: zero potential reference to sock_common",
+	.insns = {
+	BPF_SK_LOOKUP(skc_lookup_tcp),
+	BPF_MOV64_IMM(BPF_REG_0, 0), /* leak reference */
+	BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+	.errstr = "Unreleased reference",
+	.result = REJECT,
+},
 {
 	"reference tracking: copy and zero potential references",
 	.insns = {
@@ -76,6 +98,20 @@
 	.errstr = "type=sock_or_null expected=sock",
 	.result = REJECT,
 },
+{
+	"reference tracking: release reference to sock_common without check",
+	.insns = {
+	BPF_SK_LOOKUP(skc_lookup_tcp),
+	/* reference in r0 may be NULL */
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+	BPF_MOV64_IMM(BPF_REG_2, 0),
+	BPF_EMIT_CALL(BPF_FUNC_sk_release),
+	BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+	.errstr = "type=sock_common_or_null expected=sock",
+	.result = REJECT,
+},
 {
 	"reference tracking: release reference",
 	.insns = {
@@ -88,6 +124,18 @@
 	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 	.result = ACCEPT,
 },
+{
+	"reference tracking: release reference to sock_common",
+	.insns = {
+	BPF_SK_LOOKUP(skc_lookup_tcp),
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+	BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+	BPF_EMIT_CALL(BPF_FUNC_sk_release),
+	BPF_EXIT_INSN(),
+	},
+	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+	.result = ACCEPT,
+},
 {
 	"reference tracking: release reference 2",
 	.insns = {