Messages in this thread | | | From | "Jason A. Donenfeld" <> | Date | Fri, 2 Jun 2017 17:53:39 +0200 | Subject | Re: get_random_bytes returns bad randomness before seeding is complete |
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(Meanwhile...)
In my own code, I'm currently playing with a workaround that looks like this:
--- a/src/main.c +++ b/src/main.c
+#include <linux/completion.h> +#include <linux/random.h>
+struct rng_initializer { + struct completion done; + struct random_ready_callback cb; +}; +static void rng_initialized_callback(struct random_ready_callback *cb) +{ + complete(&container_of(cb, struct rng_initializer, cb)->done); +} + static int __init mod_init(void) { int ret; + struct rng_initializer rng = { + .done = COMPLETION_INITIALIZER(rng.done), + .cb = { .owner = THIS_MODULE, .func = rng_initialized_callback } + }; + + ret = add_random_ready_callback(&rng.cb); + if (!ret) + wait_for_completion(&rng.done); + else if (ret != -EALREADY) + return ret;
do_things_with_get_random_bytes_maybe();
Depending on the situation, however, I could imagine that wait_for_completion never returning, if its blocking activity that contributes to the seed actually being available, if this is called from a compiled-in module, so I find this a bit sub-optimal...
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