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Validate num_channels against tensor sizes in FILTER_BANK kernel #3602

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Validate num_channels against tensor sizes in FILTER_BANK kernel #3602

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46adb06
Validate num_channels against tensor sizes in FILTER_BANK kernel
adilburaksen Jun 18, 2026
40c32aa
signal/filter_bank: frame num_channels validation as Prepare-phase to…
adilburaksen Jul 1, 2026
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30 changes: 30 additions & 0 deletions signal/micro/kernels/filter_bank.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,16 @@ void* FilterBankInit(TfLiteContext* context, const char* buffer,
length);
params->config.num_channels = fbw.ElementAsInt32(kNumChannelsIndex);

// Guard the work-area size computation below against a non-positive
// num_channels or one large enough to overflow the multiplication (notably
// where size_t is 32 bits), which would size the work area inconsistently
// with the number of channels the kernel then processes.
if (params->config.num_channels <= 0 ||
static_cast<size_t>(params->config.num_channels) >
SIZE_MAX / sizeof(uint64_t) - 1) {
return nullptr;
}

params->work_area = static_cast<uint64_t*>(context->AllocatePersistentBuffer(
context, (params->config.num_channels + 1) * sizeof(uint64_t)));

Expand Down Expand Up @@ -99,27 +109,47 @@ TfLiteStatus FilterBankPrepare(TfLiteContext* context, TfLiteNode* node) {
TF_LITE_ENSURE(context, input != nullptr);
TF_LITE_ENSURE_EQ(context, NumDimensions(input), 1);
TF_LITE_ENSURE_TYPES_EQ(context, input->type, kTfLiteInt16);
const int channel_frequency_starts_size = ElementCount(*input->dims);
micro_context->DeallocateTempTfLiteTensor(input);

input = micro_context->AllocateTempInputTensor(node, kChWeightStartsTensor);
TF_LITE_ENSURE(context, input != nullptr);
TF_LITE_ENSURE_EQ(context, NumDimensions(input), 1);
TF_LITE_ENSURE_TYPES_EQ(context, input->type, kTfLiteInt16);
const int channel_weight_starts_size = ElementCount(*input->dims);
micro_context->DeallocateTempTfLiteTensor(input);

input = micro_context->AllocateTempInputTensor(node, kChannelWidthsTensor);
TF_LITE_ENSURE(context, input != nullptr);
TF_LITE_ENSURE_EQ(context, NumDimensions(input), 1);
TF_LITE_ENSURE_TYPES_EQ(context, input->type, kTfLiteInt16);
const int channel_widths_size = ElementCount(*input->dims);
micro_context->DeallocateTempTfLiteTensor(input);

TfLiteTensor* output =
micro_context->AllocateTempOutputTensor(node, kOutputTensor);
TF_LITE_ENSURE(context, output != nullptr);
TF_LITE_ENSURE_EQ(context, NumDimensions(output), 1);
TF_LITE_ENSURE_TYPES_EQ(context, output->type, kTfLiteUInt64);
const int output_size = ElementCount(*output->dims);
micro_context->DeallocateTempTfLiteTensor(output);

// Validate in Prepare that num_channels (from the init flexbuffer) is
// consistent with the per-channel metadata tensors and the output tensor, so
// an inconsistent topology is rejected here rather than during Eval.
// FilterbankAccumulateChannels reads indices [0, num_channels]
// (num_channels + 1 elements) of channel_frequency_starts,
// channel_weight_starts and channel_widths, and writes num_channels output
// elements (work_area[1 .. num_channels]).
auto* params = reinterpret_cast<TFLMSignalFilterBankParams*>(node->user_data);
TF_LITE_ENSURE(context, params != nullptr);
const int num_channels = params->config.num_channels;
TF_LITE_ENSURE(context, num_channels > 0);
TF_LITE_ENSURE_EQ(context, channel_frequency_starts_size, num_channels + 1);
TF_LITE_ENSURE_EQ(context, channel_weight_starts_size, num_channels + 1);
TF_LITE_ENSURE_EQ(context, channel_widths_size, num_channels + 1);
TF_LITE_ENSURE_EQ(context, output_size, num_channels);

return kTfLiteOk;
}

Expand Down
69 changes: 69 additions & 0 deletions signal/micro/kernels/filter_bank_test.cc
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Expand Up @@ -256,4 +256,73 @@ TEST(FilterBankTest, FilterBankTest16Channel) {
g_gen_data_size_filter_bank_16_channel, output));
}

// A model whose init flexbuffer declares num_channels = 32 but provides only
// 17-element (16-channel) side tensors is an inconsistent topology: without the
// Prepare check FilterbankAccumulateChannels would loop num_channels + 1 = 33
// times over the 17-element channel_weight_starts / channel_widths buffers.
// FilterBankPrepare must reject the mismatch with kTfLiteError.
TEST(FilterBankTest, FilterBankRejectsInconsistentNumChannels) {
int input1_shape[] = {1, 129};
int input2_shape[] = {1, 59};
int input3_shape[] = {1, 59};
int input4_shape[] = {1, 17};
int input5_shape[] = {1, 17};
int input6_shape[] = {1, 17};
int output_shape[] = {1, 16};

uint64_t output[16];

const uint32_t input1[] = {
645050, 4644, 3653, 24262, 56660, 43260, 50584, 57902, 31702, 5401,
45555, 34852, 8518, 43556, 13358, 19350, 40221, 18017, 27284, 64491,
60099, 17863, 11001, 29076, 32666, 65268, 50947, 28694, 32377, 30014,
25607, 22547, 45086, 10654, 46797, 8622, 47348, 43085, 5747, 51544,
50364, 6208, 20696, 59782, 14429, 60125, 37079, 32673, 63457, 60142,
34042, 11280, 1874, 33734, 62118, 13766, 54398, 47818, 50976, 46930,
25906, 59441, 25958, 59136, 1756, 18652, 29213, 13379, 51845, 1207,
55626, 27108, 43771, 35236, 3374, 40959, 47707, 41540, 34282, 27094,
36329, 13593, 65257, 47006, 46857, 1114, 37106, 18738, 25969, 15461,
2842, 36470, 32489, 61622, 23613, 29624, 32820, 30438, 9543, 6767,
23037, 52896, 12059, 32264, 11575, 42400, 43344, 27511, 16712, 6877,
4910, 50047, 61569, 57237, 48558, 2310, 22192, 7874, 46141, 64056,
61997, 7298, 31372, 25316, 683, 58940, 18755, 17898, 19196};

const int16_t input2[] = {
-2210, 1711, 3237, 1247, 2507, 61, 1019, 899, 206, 146, 2849, 2756,
1260, 1280, 1951, 213, 617, 2047, 211, 347, 2821, 3747, 150, 1924,
3962, 942, 1430, 2678, 993, 308, 3364, 2491, 954, 1308, 879, 3950,
1, 3556, 3628, 2104, 78, 1298, 1080, 342, 1337, 1639, 2352, 829,
1358, 2498, 1647, 2507, 3816, 3767, 3735, 1155, 2221, 2196, 1160};

const int16_t input3[] = {
408, 3574, 1880, 2561, 2011, 3394, 1019, 445, 3901, 343, 1874, 3846,
3566, 1830, 327, 111, 623, 1037, 2803, 1947, 1518, 661, 3239, 2351,
1257, 269, 1574, 3431, 3972, 2487, 2181, 1458, 552, 717, 679, 1031,
1738, 1782, 128, 2242, 353, 1460, 3305, 1424, 3813, 2895, 164, 272,
3886, 3135, 141, 747, 3233, 1478, 2612, 3837, 3271, 73, 1746};

const int16_t input4[] = {5, 6, 7, 9, 11, 12, 14, 16, 18,
20, 22, 25, 27, 30, 32, 35, 33};

const int16_t input5[] = {0, 1, 2, 4, 6, 7, 9, 11, 13,
15, 17, 20, 22, 25, 27, 30, 33};

const int16_t input6[] = {1, 1, 2, 2, 1, 2, 2, 2, 2, 2, 3, 2, 3, 2, 3, 3, 3};

const uint64_t golden[] = {104199304, 407748384, 206363744, 200989269,
52144406, 230780884, 174394190, 379684049,
94840835, 57788823, 531528204, 318265707,
263149795, 188110467, 501443259, 200747781};

// With the fix in FilterBankPrepare, the num_channels/tensor-size mismatch is
// rejected before Eval, so no out-of-bounds access occurs.
EXPECT_EQ(
kTfLiteError,
tflite::testing::TestFilterBank(
input1_shape, input1, input2_shape, input2, input3_shape, input3,
input4_shape, input4, input5_shape, input5, input6_shape, input6,
output_shape, golden, g_gen_data_filter_bank_32_channel,
g_gen_data_size_filter_bank_32_channel, output));
}

TF_LITE_MICRO_TESTS_MAIN