Avoid crash if read returns an error. Canonical case is on the blocking device

with concurrent readers; if someone else got the entropy first we can get
-1/errno=EAGAIN

1 files changed, 2 insertions, 1 deletions

diff --git a/src/lib/entropy/dev_random/dev_random.cpp b/src/lib/entropy/dev_random/dev_random.cpp
index 832424acd..ef6bceaf7 100644
--- a/src/lib/entropy/dev_random/dev_random.cpp
+++ b/src/lib/entropy/dev_random/dev_random.cpp
@@ -89,7 +89,8 @@ void Device_EntropySource::poll(Entropy_Accumulator& accum)
       if(FD_ISSET(m_devices[i], &read_set))
          {
          const ssize_t got = ::read(m_devices[i], &io_buffer[0], io_buffer.size());
-         accum.add(&io_buffer[0], got, ENTROPY_BITS_PER_BYTE);
+         if(got > 0)
+            accum.add(&io_buffer[0], got, ENTROPY_BITS_PER_BYTE);
          }
       }
    }