Add checks for compute_slice (#15647)

Summary:

Add safety checks to compute_slice, to ensure that we:

1. Do not read outside of the src tensor bounds
2. Do not write outside of the output tensor bounds

Differential Revision: D86433966

Author: lucylq

kernels/portable/cpu/util/slice_util.cpp

@@ -156,6 +156,14 @@ void compute_slice(
     int64_t length,
     int64_t step,
     Tensor& out) {
+  ET_CHECK_MSG(
+      dim < in.dim(),
+      "Requested dim is larger than input tensor dim; dim = %" PRId64,
+      dim);
+  ET_CHECK_MSG(start < dim, "Requested start is larger than the dim size.");
+  ET_CHECK_MSG(
+      length * step < dim,
+      "Requested length * step is larger than the dim size.");
   size_t dim_length = in.size(dim);
 
   size_t leading_dims = getLeadingDims(in, dim);
@@ -170,6 +178,9 @@ void compute_slice(
   const char* input_data = in.const_data_ptr<char>();
   char* dest = out.mutable_data_ptr<char>();
 
+  ET_CHECK_MSG(
+      out.nbytes() >= (length * leading_dims * length_per_step),
+      "out.nbytes() is smaller than the expected slice size.");
   for (const auto i : c10::irange(leading_dims)) {
     const char* src = input_data + (i * dim_length + start) * length_per_step;
     for ([[maybe_unused]] const auto j : c10::irange(length)) {