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Subject[PATCH bpf-next v2 2/2] selftests/bpf: test references to nf_conn
Date
Make sure that returning a struct nf_conn * reference invokes
the reference tracking machinery in the verifier.

Signed-off-by: Matthew Cover <matthew.cover@stackpath.com>
---
tools/testing/selftests/bpf/test_verifier.c | 18 ++++++++
.../testing/selftests/bpf/verifier/ref_tracking.c | 48 ++++++++++++++++++++++
2 files changed, 66 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 87eaa49..7569db2 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -294,6 +294,24 @@ static void bpf_fill_scale(struct bpf_test *self)
}
}

+/* BPF_CT_LOOKUP contains 13 instructions, if you need to fix up maps */
+#define BPF_CT_LOOKUP(func) \
+ /* struct bpf_nf_conntrack_tuple tuple = {} */ \
+ BPF_MOV64_IMM(BPF_REG_2, 0), \
+ BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -8), \
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -16), \
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -24), \
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -32), \
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -40), \
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -48), \
+ /* ct = func(ctx, &tuple, sizeof tuple, 0, 0) */ \
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), \
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -48), \
+ BPF_MOV64_IMM(BPF_REG_3, sizeof(struct bpf_nf_conntrack_tuple)),\
+ BPF_MOV64_IMM(BPF_REG_4, 0), \
+ BPF_MOV64_IMM(BPF_REG_5, 0), \
+ BPF_EMIT_CALL(BPF_FUNC_ ## func)
+
/* BPF_SK_LOOKUP contains 13 instructions, if you need to fix up maps */
#define BPF_SK_LOOKUP(func) \
/* struct bpf_sock_tuple tuple = {} */ \
diff --git a/tools/testing/selftests/bpf/verifier/ref_tracking.c b/tools/testing/selftests/bpf/verifier/ref_tracking.c
index 604b461..de5c550a 100644
--- a/tools/testing/selftests/bpf/verifier/ref_tracking.c
+++ b/tools/testing/selftests/bpf/verifier/ref_tracking.c
@@ -21,6 +21,17 @@
.result = REJECT,
},
{
+ "reference tracking: leak potential reference to nf_conn",
+ .insns = {
+ BPF_CT_LOOKUP(ct_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 = {
BPF_SK_LOOKUP(sk_lookup_tcp),
@@ -72,6 +83,17 @@
.result = REJECT,
},
{
+ "reference tracking: zero potential reference to nf_conn",
+ .insns = {
+ BPF_CT_LOOKUP(ct_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 = {
BPF_SK_LOOKUP(sk_lookup_tcp),
@@ -113,6 +135,20 @@
.result = REJECT,
},
{
+ "reference tracking: release reference to nf_conn without check",
+ .insns = {
+ BPF_CT_LOOKUP(ct_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_ct_release),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ .errstr = "type=nf_conn_or_null expected=nf_conn",
+ .result = REJECT,
+},
+{
"reference tracking: release reference",
.insns = {
BPF_SK_LOOKUP(sk_lookup_tcp),
@@ -137,6 +173,18 @@
.result = ACCEPT,
},
{
+ "reference tracking: release reference to nf_conn",
+ .insns = {
+ BPF_CT_LOOKUP(ct_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_ct_release),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ .result = ACCEPT,
+},
+{
"reference tracking: release reference 2",
.insns = {
BPF_SK_LOOKUP(sk_lookup_tcp),
--
1.8.3.1
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