endless loop in probable_prime

[Ronny Meeus <ronny.meeus@xxxxxxxxx>]

Hello

we are in the process of upgrading our openssl to version 1.1.1g.
On one of our architectures (Cavium MIPS, running kernel 4.9) we have
an issue in the ssh-keygen tool. It keeps on consuming 100% CPU of 1
core.
On other architectures we do not see the issue at all.

I instrumented the openssl library with some traces and observed that
it keeps on looping in the "probable prime" function.
At the end of the function the "BN_num_bits" check is done and if the
return value is not equal to "bits" it basically starts all over
again.

    }
    if (!BN_add_word(rnd, delta))
        return 0;
    if (BN_num_bits(rnd) != bits) {
        printf("%s BN_num_bits %d %d\n", __FUNCTION__, BN_num_bits(rnd), bits);
        goto again;
    }
    bn_check_top(rnd);
    return 1;
}

I added the print function and the result of the print is as follows:
probable_prime BN_num_bits 1473 1536
This trace keeps on going forever and the values never change.

Any idea what could be the underlying root-cause?

Many thanks and best regards,
Ronny