Re: Large post detailing recent Linux RNG improvements

Jason A. Donenfeld <[email protected]> wrote:

> Thought I should mention here that I've written up the various RNG
> things I've been working on for 5.17 & 5.18 here:
> https://www.zx2c4.com/projects/linux-rng-5.17-5.18/ .
>
> Feel free to discuss on list here if you'd like, or if you see
> something you don't like, I'll happily review patches!

Your code includes:

enum {
    POOL_BITS = BLAKE2S_HASH_SIZE * 8,
    POOL_MIN_BITS = POOL_BITS /* No point in settling for less. */
};

static struct {
    struct blake2s_state hash;
    spinlock_t lock;
    unsigned int entropy_count;
} input_pool = {
    .hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE),
            BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4,
            BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 },
    .hash.outlen = BLAKE2S_HASH_SIZE,
    .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
};

As far as I can tell, you have eliminated the 4K-bit input pool
that this driver has always used & are just using the hash
context as the input pool. To me, this looks like an error.

A side effect of that is losing the latent-entropy attribute
on input_pool[] so we no longer get initialisation from
the plugin. Another error.