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Commit d3cc7996 authored by Amit Shah's avatar Amit Shah Committed by Herbert Xu
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hwrng: fetch randomness only after device init 



Commit d9e79726 "hwrng: add randomness to system from rng sources"
added a call to rng_get_data() from the hwrng_register() function.
However, some rng devices need initialization before data can be read
from them.

This commit makes the call to rng_get_data() depend on no init fn
pointer being registered by the device.  If an init function is
registered, this call is made after device init.

CC: Kees Cook <keescook@chromium.org>
CC: Jason Cooper <jason@lakedaemon.net>
CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: <stable@vger.kernel.org> # For v3.15+
Signed-off-by: default avatarAmit Shah <amit.shah@redhat.com>
Reviewed-by: default avatarJason Cooper <jason@lakedaemon.net>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 0378c9a8

drivers/char/hw_random/core.c

+33 −8
Original line number Diff line number Diff line
@@ -55,16 +55,35 @@ static DEFINE_MUTEX(rng_mutex); 
static int data_avail;

static u8 *rng_buffer;



static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,

			       int wait);



static size_t rng_buffer_size(void)

{

	return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;

}



static void add_early_randomness(struct hwrng *rng)

{

	unsigned char bytes[16];

	int bytes_read;



	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);

	if (bytes_read > 0)

		add_device_randomness(bytes, bytes_read);

}



static inline int hwrng_init(struct hwrng *rng)

{

	if (!rng->init)

	if (rng->init) {

		int ret;



		ret =  rng->init(rng);

		if (ret)

			return ret;

	}

	add_early_randomness(rng);

	return 0;

	return rng->init(rng);

}



static inline void hwrng_cleanup(struct hwrng *rng)
@@ -304,8 +323,6 @@ int hwrng_register(struct hwrng *rng) 
{

	int err = -EINVAL;

	struct hwrng *old_rng, *tmp;

	unsigned char bytes[16];

	int bytes_read;



	if (rng->name == NULL ||

	    (rng->data_read == NULL && rng->read == NULL))
@@ -347,9 +364,17 @@ int hwrng_register(struct hwrng *rng) 
	INIT_LIST_HEAD(&rng->list);

	list_add_tail(&rng->list, &rng_list);



	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);

	if (bytes_read > 0)

		add_device_randomness(bytes, bytes_read);

	if (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.

		 */

		add_early_randomness(rng);

	}



out_unlock:

	mutex_unlock(&rng_mutex);

out: