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52 lines
2.0 KiB
Markdown
52 lines
2.0 KiB
Markdown
## TFSA-2020-016: Segfault due to invalid splits in RaggedCountSparseOutput
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### CVE Number
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CVE-2020-15200
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### Impact
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The `RaggedCountSparseOutput` implementation does not validate that the input
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arguments form a valid ragged tensor. In particular, there is no validation that
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the values in the `splits` tensor generate a valid partitioning of the `values`
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tensor. Thus, the [following
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code](https://github.com/tensorflow/tensorflow/blob/0e68f4d3295eb0281a517c3662f6698992b7b2cf/tensorflow/core/kernels/count_ops.cc#L248-L265
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) sets up conditions to cause a heap buffer overflow:
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```cc
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auto per_batch_counts = BatchedMap<W>(num_batches);
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int batch_idx = 0;
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for (int idx = 0; idx < num_values; ++idx) {
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while (idx >= splits_values(batch_idx)) {
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batch_idx++;
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}
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const auto& value = values_values(idx);
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if (value >= 0 && (maxlength_ <= 0 || value < maxlength_)) {
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per_batch_counts[batch_idx - 1][value] = 1;
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}
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}
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```
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A `BatchedMap` is equivalent to a vector where each element is a hashmap.
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However, if the first element of `splits_values` is not 0, `batch_idx` will
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never be 1, hence there will be no hashmap at index 0 in `per_batch_counts`.
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Trying to access that in the user code results in a segmentation fault.
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### Vulnerable Versions
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TensorFlow 2.3.0.
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### Patches
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We have patched the issue in
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[3cbb917b4714766030b28eba9fb41bb97ce9ee02](https://github.com/tensorflow/tensorflow/commit/3cbb917b4714766030b28eba9fb41bb97ce9ee02)
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and will release a patch release.
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We recommend users to upgrade to TensorFlow 2.3.1.
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### For more information
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Please consult [our security
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guide](https://github.com/tensorflow/tensorflow/blob/master/SECURITY.md) for
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more information regarding the security model and how to contact us with issues
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and questions.
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### Attribution
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This vulnerability has been discovered through a variant analysis of [a
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vulnerability reported by members of the Aivul Team from Qihoo
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360](https://github.com/tensorflow/tensorflow/blob/master/tensorflow/security/advisory/tfsa-2020-015.md).
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