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Fix #3505: Prevent undefined behavior due to incorrectly sized base_margin (#3555)

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The base margin will need to have length `[num_class] * [number of data points]`.
Otherwise, the array holding prediction results will be only partially
initialized, causing undefined behavior.

Fix: check the length of the base margin. If the length is not correct,
use the global bias (`base_score`) instead. Warn the user about the
substitution.
This commit is contained in:
Philip Hyunsu Cho 2018-08-05 10:14:07 -07:00 committed by GitHub
parent 4a429a7c4f
commit 8c633d1ca3
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1 changed files with 16 additions and 1 deletions
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17
src/predictor/cpu_predictor.cc
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@ -131,10 +131,25 @@ class CPUPredictor : public Predictor {
const std::vector<bst_float>& base_margin = info.base_margin_; const std::vector<bst_float>& base_margin = info.base_margin_;
out_preds->Resize(n); out_preds->Resize(n);
std::vector<bst_float>& out_preds_h = out_preds->HostVector(); std::vector<bst_float>& out_preds_h = out_preds->HostVector();
if (base_margin.size() != 0) { if (base_margin.size() == n) {
CHECK_EQ(out_preds->Size(), n); CHECK_EQ(out_preds->Size(), n);
std::copy(base_margin.begin(), base_margin.end(), out_preds_h.begin()); std::copy(base_margin.begin(), base_margin.end(), out_preds_h.begin());
} else { } else {
if (!base_margin.empty()) {
std::ostringstream oss;
oss << "Warning: Ignoring the base margin, since it has incorrect length. "
<< "The base margin must be an array of length ";
if (model.param.num_output_group > 1) {
oss << "[num_class] * [number of data points], i.e. "
<< model.param.num_output_group << " * " << info.num_row_
<< " = " << n << ". ";
} else {
oss << "[number of data points], i.e. " << info.num_row_ << ". ";
}
oss << "Instead, all data points will use "
<< "base_score = " << model.base_margin;
LOG(INFO) << oss.str();
}
std::fill(out_preds_h.begin(), out_preds_h.end(), model.base_margin); std::fill(out_preds_h.begin(), out_preds_h.end(), model.base_margin);
} }
} }