fec: Fix input buffer overrun in polar encoder

Signed-off-by: Clayton Smith <argilo@gmail.com>
(cherry picked from commit 23e58b2894b541e174fc235d253cc424299a09bf)
Signed-off-by: Jeff Long <willcode4@gmail.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/gr-fec/lib/polar_encoder.cc b/gr-fec/lib/polar_encoder.cc
index 84633ec89..465f0c968 100644
--- a/gr-fec/lib/polar_encoder.cc
+++ b/gr-fec/lib/polar_encoder.cc
@@ -132,17 +132,17 @@ void polar_encoder::insert_packed_frozen_bits_and_reverse(
         std::begin(d_frozen_bit_prototype), std::end(d_frozen_bit_prototype), target);
     const int* info_bit_reversed_positions_ptr = &d_info_bit_positions_reversed[0];
     int bit_num = 0;
-    unsigned char byte = *input;
+    unsigned char byte;
     int bit_pos;
     while (bit_num < num_info_bits()) {
+        if (bit_num % 8 == 0) {
+            byte = *input;
+            ++input;
+        }
         bit_pos = *info_bit_reversed_positions_ptr++;
         insert_packet_bit_into_packed_array_at_position(
             target, byte, bit_pos, bit_num % 8);
         ++bit_num;
-        if (bit_num % 8 == 0) {
-            ++input;
-            byte = *input;
-        }
     }
 }