selftests/bpf: add tests for stack_zero tracking

adjust two tests, since verifier got smarter
and add new one to test stack_zero logic

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 64 insertions, 2 deletions

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 88f389c6ec48..eaf294822a8f 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -5649,7 +5649,7 @@ static struct bpf_test tests[] = {
                 "helper access to variable memory: size > 0 not allowed on NULL (ARG_PTR_TO_MEM_OR_NULL)",
                 .insns = {
                         BPF_MOV64_IMM(BPF_REG_1, 0),
-                        BPF_MOV64_IMM(BPF_REG_2, 0),
+                        BPF_MOV64_IMM(BPF_REG_2, 1),
                         BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -128),
                         BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_10, -128),
                         BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 64),
@@ -5884,7 +5884,7 @@ static struct bpf_test tests[] = {
                         BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -24),
                         BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -16),
                         BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8),
-                        BPF_MOV64_IMM(BPF_REG_2, 0),
+                        BPF_MOV64_IMM(BPF_REG_2, 1),
                         BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -128),
                         BPF_LDX_MEM(BPF_DW, BPF_REG_2, BPF_REG_10, -128),
                         BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 63),
@@ -9056,6 +9056,68 @@ static struct bpf_test tests[] = {
                 .result = ACCEPT,
                 .prog_type = BPF_PROG_TYPE_SCHED_CLS,
         },
+        {
+                "calls: caller stack init to zero or map_value_or_null",
+                .insns = {
+                        BPF_MOV64_IMM(BPF_REG_0, 0),
+                        BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8),
+                        BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+                        BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+                        BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 4),
+                        /* fetch map_value_or_null or const_zero from stack */
+                        BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_10, -8),
+                        BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+                        /* store into map_value */
+                        BPF_ST_MEM(BPF_W, BPF_REG_0, 0, 0),
+                        BPF_EXIT_INSN(),
+
+                        /* subprog 1 */
+                        /* if (ctx == 0) return; */
+                        BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0, 8),
+                        /* else bpf_map_lookup() and *(fp - 8) = r0 */
+                        BPF_MOV64_REG(BPF_REG_6, BPF_REG_2),
+                        BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+                        BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+                        BPF_LD_MAP_FD(BPF_REG_1, 0),
+                        BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+                        BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+                                     BPF_FUNC_map_lookup_elem),
+                        /* write map_value_ptr_or_null into stack frame of main prog at fp-8 */
+                        BPF_STX_MEM(BPF_DW, BPF_REG_6, BPF_REG_0, 0),
+                        BPF_EXIT_INSN(),
+                },
+                .fixup_map1 = { 13 },
+                .result = ACCEPT,
+                .prog_type = BPF_PROG_TYPE_XDP,
+        },
+        {
+                "calls: stack init to zero and pruning",
+                .insns = {
+                        /* first make allocated_stack 16 byte */
+                        BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0),
+                        /* now fork the execution such that the false branch
+                         * of JGT insn will be verified second and it skisp zero
+                         * init of fp-8 stack slot. If stack liveness marking
+                         * is missing live_read marks from call map_lookup
+                         * processing then pruning will incorrectly assume
+                         * that fp-8 stack slot was unused in the fall-through
+                         * branch and will accept the program incorrectly
+                         */
+                        BPF_JMP_IMM(BPF_JGT, BPF_REG_1, 2, 2),
+                        BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+                        BPF_JMP_IMM(BPF_JA, 0, 0, 0),
+                        BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+                        BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+                        BPF_LD_MAP_FD(BPF_REG_1, 0),
+                        BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+                                     BPF_FUNC_map_lookup_elem),
+                        BPF_EXIT_INSN(),
+                },
+                .fixup_map2 = { 6 },
+                .errstr = "invalid indirect read from stack off -8+0 size 8",
+                .result = REJECT,
+                .prog_type = BPF_PROG_TYPE_XDP,
+        },
 };
 
 static int probe_filter_length(const struct bpf_insn *fp)