From patchwork Fri Nov 18 13:32:37 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. 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Donenfeld" To: linux-efi@vger.kernel.org, linux-crypto@vger.kernel.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org Cc: "Jason A. Donenfeld" Subject: [PATCH v2 3/5] random: add back async readiness notifier Date: Fri, 18 Nov 2022 14:32:37 +0100 Message-Id: <20221118133239.2515648-4-Jason@zx2c4.com> In-Reply-To: <20221118133239.2515648-1-Jason@zx2c4.com> References: <20221118133239.2515648-1-Jason@zx2c4.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org This is required by vsprint, because it can't do things synchronously from hardirq context, and it will be useful for an EFI notifier as well. I didn't initially want to do this, but with two potential consumers now, it seems worth it. Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 20 ++++++++++++++++++++ include/linux/random.h | 1 + 2 files changed, 21 insertions(+) diff --git a/drivers/char/random.c b/drivers/char/random.c index 65ee69896967..1185fe11b719 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -84,6 +84,7 @@ static DEFINE_STATIC_KEY_FALSE(crng_is_ready); /* Various types of waiters for crng_init->CRNG_READY transition. */ static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait); static struct fasync_struct *fasync; +static ATOMIC_NOTIFIER_HEAD(random_ready_notifier); /* Control how we warn userspace. */ static struct ratelimit_state urandom_warning = @@ -140,6 +141,24 @@ int wait_for_random_bytes(void) } EXPORT_SYMBOL(wait_for_random_bytes); +/* + * Add a callback function that will be invoked when the crng is initialised, + * or immediately if it already has been. + */ +int __cold execute_with_initialized_rng(struct notifier_block *nb) +{ + unsigned long flags; + int ret = 0; + + spin_lock_irqsave(&random_ready_notifier.lock, flags); + if (crng_ready()) + nb->notifier_call(nb, 0, NULL); + else + ret = raw_notifier_chain_register((struct raw_notifier_head *)&random_ready_notifier.head, nb); + spin_unlock_irqrestore(&random_ready_notifier.lock, flags); + return ret; +} + #define warn_unseeded_randomness() \ if (IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM) && !crng_ready()) \ printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", \ @@ -697,6 +716,7 @@ static void __cold _credit_init_bits(size_t bits) crng_reseed(NULL); /* Sets crng_init to CRNG_READY under base_crng.lock. */ if (static_key_initialized) execute_in_process_context(crng_set_ready, &set_ready); + atomic_notifier_call_chain(&random_ready_notifier, 0, NULL); wake_up_interruptible(&crng_init_wait); kill_fasync(&fasync, SIGIO, POLL_IN); pr_notice("crng init done\n"); diff --git a/include/linux/random.h b/include/linux/random.h index 579117d83eb8..b1a34181eed6 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -120,6 +120,7 @@ void __init random_init_early(const char *command_line); void __init random_init(void); bool rng_is_initialized(void); int wait_for_random_bytes(void); +int execute_with_initialized_rng(struct notifier_block *nb); /* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes). * Returns the result of the call to wait_for_random_bytes. */