Verify that nullness information is porpagated in the branches of
register to register JEQ and JNE operations.
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
---
.../bpf/verifier/jeq_infer_not_null.c | 174 ++++++++++++++++++
1 file changed, 174 insertions(+)
create mode 100644 tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c
diff --git a/tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c b/tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c
new file mode 100644
index 000000000000..67a1c07ead34
--- /dev/null
+++ b/tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c
@@ -0,0 +1,174 @@
+{
+ /* This is equivalent to the following program:
+ *
+ * r6 = skb->sk;
+ * r7 = sk_fullsock(r6);
+ * r0 = sk_fullsock(r6);
+ * if (r0 == 0) return 0; (a)
+ * if (r0 != r7) return 0; (b)
+ * *r7->type; (c)
+ * return 0;
+ *
+ * It is safe to dereference r7 at point (c), because of (a) and (b).
+ * The test verifies that relation r0 == r7 is propagated from (b) to (c).
+ */
+ "jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL -> PTR_TO_SOCKET for JNE false branch",
+ .insns = {
+ /* r6 = skb->sk; */
+ BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)),
+ /* if (r6 == 0) return 0; */
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 8),
+ /* r7 = sk_fullsock(skb); */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
+ /* r0 = sk_fullsock(skb); */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ /* if (r0 == null) return 0; */
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
+ /* if (r0 == r7) r0 = *(r7->type); */
+ BPF_JMP_REG(BPF_JNE, BPF_REG_0, BPF_REG_7, 1), /* Use ! JNE ! */
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)),
+ /* return 0 */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+ .result = ACCEPT,
+ .result_unpriv = REJECT,
+ .errstr_unpriv = "R7 pointer comparison",
+},
+{
+ /* Same as above, but verify that another branch of JNE still
+ * prohibits access to PTR_MAYBE_NULL.
+ */
+ "jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL unchanged for JNE true branch",
+ .insns = {
+ /* r6 = skb->sk */
+ BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)),
+ /* if (r6 == 0) return 0; */
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 9),
+ /* r7 = sk_fullsock(skb); */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
+ /* r0 = sk_fullsock(skb); */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ /* if (r0 == null) return 0; */
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 3),
+ /* if (r0 == r7) return 0; */
+ BPF_JMP_REG(BPF_JNE, BPF_REG_0, BPF_REG_7, 1), /* Use ! JNE ! */
+ BPF_JMP_IMM(BPF_JA, 0, 0, 1),
+ /* r0 = *(r7->type); */
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)),
+ /* return 0 */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+ .result = REJECT,
+ .errstr = "R7 invalid mem access 'sock_or_null'",
+ .result_unpriv = REJECT,
+ .errstr_unpriv = "R7 pointer comparison",
+},
+{
+ /* Same as a first test, but not null should be inferred for JEQ branch */
+ "jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL -> PTR_TO_SOCKET for JEQ true branch",
+ .insns = {
+ /* r6 = skb->sk; */
+ BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)),
+ /* if (r6 == null) return 0; */
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 9),
+ /* r7 = sk_fullsock(skb); */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
+ /* r0 = sk_fullsock(skb); */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ /* if (r0 == null) return 0; */
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 3),
+ /* if (r0 != r7) return 0; */
+ BPF_JMP_REG(BPF_JEQ, BPF_REG_0, BPF_REG_7, 1), /* Use ! JEQ ! */
+ BPF_JMP_IMM(BPF_JA, 0, 0, 1),
+ /* r0 = *(r7->type); */
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)),
+ /* return 0; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+ .result = ACCEPT,
+ .result_unpriv = REJECT,
+ .errstr_unpriv = "R7 pointer comparison",
+},
+{
+ /* Same as above, but verify that another branch of JNE still
+ * prohibits access to PTR_MAYBE_NULL.
+ */
+ "jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL unchanged for JEQ false branch",
+ .insns = {
+ /* r6 = skb->sk; */
+ BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)),
+ /* if (r6 == null) return 0; */
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 8),
+ /* r7 = sk_fullsock(skb); */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
+ /* r0 = sk_fullsock(skb); */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+ BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
+ /* if (r0 == null) return 0; */
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
+ /* if (r0 != r7) r0 = *(r7->type); */
+ BPF_JMP_REG(BPF_JEQ, BPF_REG_0, BPF_REG_7, 1), /* Use ! JEQ ! */
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)),
+ /* return 0; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+ .result = REJECT,
+ .errstr = "R7 invalid mem access 'sock_or_null'",
+ .result_unpriv = REJECT,
+ .errstr_unpriv = "R7 pointer comparison",
+},
+{
+ /* Maps are treated in a different branch of `mark_ptr_not_null_reg`,
+ * so separate test for maps case.
+ */
+ "jne/jeq infer not null, PTR_TO_MAP_VALUE_OR_NULL -> PTR_TO_MAP_VALUE",
+ .insns = {
+ /* r9 = &some stack to use as key */
+ BPF_ST_MEM(BPF_W, BPF_REG_10, -8, 0),
+ BPF_MOV64_REG(BPF_REG_9, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_9, -8),
+ /* r8 = process local map */
+ BPF_LD_MAP_FD(BPF_REG_8, 0),
+ /* r6 = map_lookup_elem(r8, r9); */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_8),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_9),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
+ /* r7 = map_lookup_elem(r8, r9); */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_8),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_9),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
+ /* if (r6 == 0) return 0; */
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 2),
+ /* if (r6 != r7) return 0; */
+ BPF_JMP_REG(BPF_JNE, BPF_REG_6, BPF_REG_7, 1),
+ /* read *r7; */
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_xdp_sock, queue_id)),
+ /* return 0; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map_xskmap = { 3 },
+ .prog_type = BPF_PROG_TYPE_XDP,
+ .result = ACCEPT,
+},
--
2.34.1
