Martin Panter (msg267504): "As I understand it, if there is no entropy initialized, this patch will fall back to reading /dev/urandom, which will return predictable data (opposite of “random” data!)."

No, I don't think so.

Linux uses a lot of random sources, but some of them are seen as untrusted as so are added with a very low estimation of their entropy. Linux even adds some random values with a estimation of 0 bit of entropy. For example, drivers can add serial numbers as random numbers.

So even if getrandom() blocks, if the urandom entropy pool is not considered as fully initialized yet, I expect that /dev/urandom still generates *random* numbers, even if these numbers are not suitable to generate cryptographic keys.

Please double check, I'm not sure of what I wrote :-)

See also http://www.2uo.de/myths-about-urandom/ (but this article doesn't describe how urandom is initialized).