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44 lines
1.8 KiB
Markdown
44 lines
1.8 KiB
Markdown
## TFSA-2020-009: Segfault and data corruption caused by negative indexing in TFLite
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### CVE Number
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CVE-2020-15207
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### Impact
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To mimic Python's indexing with negative values, TFLite uses `ResolveAxis` to
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convert negative values to positive indices. However, the only check that the
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converted index is now valid is [only present in debug
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builds](https://github.com/tensorflow/tensorflow/blob/0e68f4d3295eb0281a517c3662f6698992b7b2cf/tensorflow/lite/kernels/internal/reference/reduce.h#L68-L72):
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```cc
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// Handle negative index. A positive index 'p_idx' can be represented as a
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// negative index 'n_idx' as: n_idx = p_idx-num_dims
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// eg: For num_dims=3, [0, 1, 2] is the same as [-3, -2, -1] */
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int current = axis[idx] < 0 ? (axis[idx] + num_dims) : axis[idx];
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TFLITE_DCHECK(current >= 0 && current < num_dims);
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```
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If the `DCHECK` does not trigger, then code execution moves ahead with a
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negative index. This, in turn, results in accessing data out of bounds which
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results in segfaults and/or data corruption.
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### Vulnerable Versions
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TensorFlow 1.15.0, 1.15.1, 1.15.2, 1.15.3, 2.0.0, 2.0.1, 2.0.2, 2.1.0, 2.1.1,
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2.2.0, 2.3.0.
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### Patches
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We have patched the issue in
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[2d88f470dea2671b430884260f3626b1fe99830a](https://github.com/tensorflow/tensorflow/commit/2d88f470dea2671b430884260f3626b1fe99830a)
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and will release patch releases for all versions between 1.15 and 2.3.
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We recommend users to upgrade to TensorFlow 1.15.4, 2.0.3, 2.1.2, 2.2.1, or
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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 reported by members of the Aivul Team from Qihoo
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360.
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