[PATCH] hwrng: core - Allocate memory during module init

[PATCH] hwrng: core - Allocate memory during module init

[PrasannaKumar Muralidharan]

In core rng_buffer and rng_fillbuf is allocated in hwrng_register only
once and it is freed during module exit. This patch moves allocating
rng_buffer and rng_fillbuf from hwrng_register to rng core's init. This
avoids checking whether rng_buffer and rng_fillbuf was allocated from
every hwrng_register call. Also moving them to module init makes it
explicit that it is freed in module exit.

Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
---
 drivers/char/hw_random/core.c | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 9203f2d..ec6846b 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -449,22 +449,6 @@ int hwrng_register(struct hwrng *rng)
 		goto out;
 
 	mutex_lock(&rng_mutex);
-
-	/* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
-	err = -ENOMEM;
-	if (!rng_buffer) {
-		rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
-		if (!rng_buffer)
-			goto out_unlock;
-	}
-	if (!rng_fillbuf) {
-		rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
-		if (!rng_fillbuf) {
-			kfree(rng_buffer);
-			goto out_unlock;
-		}
-	}
-
 	/* Must not register two RNGs with the same name. */
 	err = -EEXIST;
 	list_for_each_entry(tmp, &rng_list, list) {
@@ -573,6 +557,17 @@ EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
 
 static int __init hwrng_modinit(void)
 {
+	/* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
+	rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
+	if (!rng_buffer)
+		return -ENOMEM;
+
+	rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
+	if (!rng_fillbuf) {
+		kfree(rng_buffer);
+		return -ENOMEM;
+	}
+
 	return register_miscdev();
 }
 
-- 
2.5.0

Re: [PATCH] hwrng: core - Allocate memory during module init

[Herbert Xu]

On Sun, Sep 04, 2016 at 01:59:38PM +0530, PrasannaKumar Muralidharan wrote:
>
> @@ -573,6 +557,17 @@ EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
>  
>  static int __init hwrng_modinit(void)
>  {
> +	/* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
> +	rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
> +	if (!rng_buffer)
> +		return -ENOMEM;
> +
> +	rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
> +	if (!rng_fillbuf) {
> +		kfree(rng_buffer);
> +		return -ENOMEM;
> +	}
> +
>  	return register_miscdev();

You're leaking memory if register_miscdev fails.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH] hwrng: core - Allocate memory during module init

[PrasannaKumar Muralidharan]

> On Sun, Sep 04, 2016 at 01:59:38PM +0530, PrasannaKumar Muralidharan wrote:
>>
>> @@ -573,6 +557,17 @@ EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
>>
>>  static int __init hwrng_modinit(void)
>>  {
>> +     /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
>> +     rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
>> +     if (!rng_buffer)
>> +             return -ENOMEM;
>> +
>> +     rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
>> +     if (!rng_fillbuf) {
>> +             kfree(rng_buffer);
>> +             return -ENOMEM;
>> +     }
>> +
>>       return register_miscdev();
>
> You're leaking memory if register_miscdev fails.

Ah, yes! I can send a revised patch.
Do you think allocating rng_buffer, rng_fillbuf in module init useful?
If not there is no point in sending a new patch with fix.

Thanks,
PrasannaKumar

Re: [PATCH] hwrng: core - Allocate memory during module init

[Herbert Xu]

On Wed, Sep 07, 2016 at 06:44:32PM +0530, PrasannaKumar Muralidharan wrote:
>
> Ah, yes! I can send a revised patch.
> Do you think allocating rng_buffer, rng_fillbuf in module init useful?
> If not there is no point in sending a new patch with fix.

Yes I think it makes sense.  Those who want to save a few bytes
by keeping the RNGs as modules can always build core HWRNG as a
module too.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt