On Sun, Jan 1, 2023 at 12:34 AM Kumar Kartikeya Dwivedi
<memxor@xxxxxxxxx> wrote:
>
> Add verifier tests that verify the new pruning behavior for STACK_DYNPTR
> slots, and ensure that state equivalence takes into account changes to
> the old and current verifier state correctly.
>
> Without the prior fixes, both of these bugs trigger with unprivileged
> BPF mode.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> ---
> tools/testing/selftests/bpf/verifier/dynptr.c | 90 +++++++++++++++++++
> 1 file changed, 90 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/verifier/dynptr.c
>
> diff --git a/tools/testing/selftests/bpf/verifier/dynptr.c b/tools/testing/selftests/bpf/verifier/dynptr.c
> new file mode 100644
> index 000000000000..798f4f7e0c57
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/verifier/dynptr.c
> @@ -0,0 +1,90 @@
> +{
> + "dynptr: rewrite dynptr slot",
> + .insns = {
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_LD_MAP_FD(BPF_REG_6, 0),
> + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
> + BPF_MOV64_IMM(BPF_REG_2, 8),
> + BPF_MOV64_IMM(BPF_REG_3, 0),
> + BPF_MOV64_REG(BPF_REG_4, BPF_REG_10),
> + BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, -16),
> + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve_dynptr),
> + BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
> + BPF_JMP_IMM(BPF_JA, 0, 0, 1),
> + BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0xeB9F),
> + BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
> + BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -16),
> + BPF_MOV64_IMM(BPF_REG_2, 0),
> + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_discard_dynptr),
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_EXIT_INSN(),
> + },
> + .fixup_map_ringbuf = { 1 },
> + .result_unpriv = REJECT,
> + .errstr_unpriv = "unknown func bpf_ringbuf_reserve_dynptr#198",
> + .result = REJECT,
> + .errstr = "arg 1 is an unacquired reference",
> +},
> +{
> + "dynptr: type confusion",
> + .insns = {
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_LD_MAP_FD(BPF_REG_6, 0),
> + BPF_LD_MAP_FD(BPF_REG_7, 0),
> + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
> + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
> + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
> + BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
> + BPF_MOV64_REG(BPF_REG_3, BPF_REG_10),
> + BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -24),
> + BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0xeB9FeB9F),
> + BPF_ST_MEM(BPF_DW, BPF_REG_10, -24, 0xeB9FeB9F),
> + BPF_MOV64_IMM(BPF_REG_4, 0),
> + BPF_MOV64_REG(BPF_REG_8, BPF_REG_2),
> + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_update_elem),
> + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
> + BPF_MOV64_REG(BPF_REG_2, BPF_REG_8),
> + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
> + BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
> + BPF_EXIT_INSN(),
> + BPF_MOV64_REG(BPF_REG_8, BPF_REG_0),
> + BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
> + BPF_MOV64_IMM(BPF_REG_2, 8),
> + BPF_MOV64_IMM(BPF_REG_3, 0),
> + BPF_MOV64_REG(BPF_REG_4, BPF_REG_10),
> + BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, -16),
> + BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
> + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve_dynptr),
> + BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 8),
> + /* pad with insns to trigger add_new_state heuristic for straight line path */
> + BPF_MOV64_REG(BPF_REG_8, BPF_REG_8),
> + BPF_MOV64_REG(BPF_REG_8, BPF_REG_8),
> + BPF_MOV64_REG(BPF_REG_8, BPF_REG_8),
> + BPF_MOV64_REG(BPF_REG_8, BPF_REG_8),
> + BPF_MOV64_REG(BPF_REG_8, BPF_REG_8),
> + BPF_MOV64_REG(BPF_REG_8, BPF_REG_8),
> + BPF_MOV64_REG(BPF_REG_8, BPF_REG_8),
> + BPF_JMP_IMM(BPF_JA, 0, 0, 9),
> + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
> + BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0),
> + BPF_MOV64_REG(BPF_REG_1, BPF_REG_8),
> + BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 8),
> + BPF_MOV64_IMM(BPF_REG_2, 0),
> + BPF_MOV64_IMM(BPF_REG_3, 0),
> + BPF_MOV64_REG(BPF_REG_4, BPF_REG_10),
> + BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, -16),
> + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_dynptr_from_mem),
> + BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
> + BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -16),
> + BPF_MOV64_IMM(BPF_REG_2, 0),
> + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_discard_dynptr),
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_EXIT_INSN(),
> + },
> + .fixup_map_hash_16b = { 1 },
> + .fixup_map_ringbuf = { 3 },
> + .result_unpriv = REJECT,
> + .errstr_unpriv = "unknown func bpf_ringbuf_reserve_dynptr#198",
> + .result = REJECT,
> + .errstr = "arg 1 is an unacquired reference",
> +},
have you tried to write these tests as embedded assembly in .bpf.c,
using __attribute__((naked)) and __failure and __msg("")
infrastructure? Eduard is working towards converting test_verifier's
test to this __naked + embed asm approach, so we might want to start
adding new tests in such form anyways? And they will be way more
readable. Defining and passing ringbuf map in C is also much more
obvious and easy.
> --
> 2.39.0
>
