Commit daae28de authored by Laurent Vivier's avatar Laurent Vivier Committed by Herbert Xu
Browse files

hwrng: core - move add_early_randomness() out of rng_mutex 



add_early_randomness() is called every time a new rng backend is added
and every time it is set as the current rng provider.

add_early_randomness() is called from functions locking rng_mutex,
and if it hangs all the hw_random framework hangs: we can't read sysfs,
add or remove a backend.

This patch move add_early_randomness() out of the rng_mutex zone.
It only needs the reading_mutex.

Signed-off-by: default avatarLaurent Vivier <lvivier@redhat.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent eff9771d

drivers/char/hw_random/core.c

+44 −16
Original line number Diff line number Diff line
@@ -112,6 +112,14 @@ static void drop_current_rng(void) 
}



/* Returns ERR_PTR(), NULL or refcounted hwrng */

static struct hwrng *get_current_rng_nolock(void)

{

	if (current_rng)

		kref_get(&current_rng->ref);



	return current_rng;

}



static struct hwrng *get_current_rng(void)

{

	struct hwrng *rng;
@@ -119,9 +127,7 @@ static struct hwrng *get_current_rng(void) 
	if (mutex_lock_interruptible(&rng_mutex))

		return ERR_PTR(-ERESTARTSYS);



	rng = current_rng;

	if (rng)

		kref_get(&rng->ref);

	rng = get_current_rng_nolock();



	mutex_unlock(&rng_mutex);

	return rng;
@@ -156,8 +162,6 @@ static int hwrng_init(struct hwrng *rng) 
	reinit_completion(&rng->cleanup_done);



skip_init:

	add_early_randomness(rng);



	current_quality = rng->quality ? : default_quality;

	if (current_quality > 1024)

		current_quality = 1024;
@@ -321,12 +325,13 @@ static ssize_t hwrng_attr_current_store(struct device *dev, 
					const char *buf, size_t len)

{

	int err = -ENODEV;

	struct hwrng *rng;

	struct hwrng *rng, *old_rng, *new_rng;



	err = mutex_lock_interruptible(&rng_mutex);

	if (err)

		return -ERESTARTSYS;



	old_rng = current_rng;

	if (sysfs_streq(buf, "")) {

		err = enable_best_rng();

	} else {
@@ -338,9 +343,15 @@ static ssize_t hwrng_attr_current_store(struct device *dev, 
			}

		}

	}



	new_rng = get_current_rng_nolock();

	mutex_unlock(&rng_mutex);



	if (new_rng) {

		if (new_rng != old_rng)

			add_early_randomness(new_rng);

		put_rng(new_rng);

	}



	return err ? : len;

}
@@ -460,13 +471,17 @@ static void start_khwrngd(void) 
int hwrng_register(struct hwrng *rng)

{

	int err = -EINVAL;

	struct hwrng *old_rng, *tmp;

	struct hwrng *old_rng, *new_rng, *tmp;

	struct list_head *rng_list_ptr;



	if (!rng->name || (!rng->data_read && !rng->read))

		goto out;



	mutex_lock(&rng_mutex);



	old_rng = current_rng;

	new_rng = NULL;



	/* Must not register two RNGs with the same name. */

	err = -EEXIST;

	list_for_each_entry(tmp, &rng_list, list) {
@@ -485,7 +500,6 @@ int hwrng_register(struct hwrng *rng) 
	}

	list_add_tail(&rng->list, rng_list_ptr);



	old_rng = current_rng;

	err = 0;

	if (!old_rng ||

	    (!cur_rng_set_by_user && rng->quality > old_rng->quality)) {
@@ -499,19 +513,24 @@ int hwrng_register(struct hwrng *rng) 
			goto out_unlock;

	}



	if (old_rng && !rng->init) {

	new_rng = rng;

	kref_get(&new_rng->ref);

out_unlock:

	mutex_unlock(&rng_mutex);



	if (new_rng) {

		if (new_rng != old_rng || !rng->init) {

		/*

		 * Use a new device's input to add some randomness to

		 * the system.  If this rng device isn't going to be

		 * used right away, its init function hasn't been

		 * called yet; so only use the randomness from devices

		 * that don't need an init callback.

		 * called yet by set_current_rng(); so only use the

		 * randomness from devices that don't need an init callback

		 */

		add_early_randomness(rng);

			add_early_randomness(new_rng);

		}

		put_rng(new_rng);

	}



out_unlock:

	mutex_unlock(&rng_mutex);

out:

	return err;

}
@@ -519,10 +538,12 @@ EXPORT_SYMBOL_GPL(hwrng_register); 


void hwrng_unregister(struct hwrng *rng)

{

	struct hwrng *old_rng, *new_rng;

	int err;



	mutex_lock(&rng_mutex);



	old_rng = current_rng;

	list_del(&rng->list);

	if (current_rng == rng) {

		err = enable_best_rng();
@@ -532,6 +553,7 @@ void hwrng_unregister(struct hwrng *rng) 
		}

	}



	new_rng = get_current_rng_nolock();

	if (list_empty(&rng_list)) {

		mutex_unlock(&rng_mutex);

		if (hwrng_fill)
@@ -539,6 +561,12 @@ void hwrng_unregister(struct hwrng *rng) 
	} else

		mutex_unlock(&rng_mutex);



	if (new_rng) {

		if (old_rng != new_rng)

			add_early_randomness(new_rng);

		put_rng(new_rng);

	}



	wait_for_completion(&rng->cleanup_done);

}

EXPORT_SYMBOL_GPL(hwrng_unregister);

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