2016-09-04 08:32:10

by PrasannaKumar Muralidharan

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

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 <[email protected]>
---
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

2016-09-07 12:54:12

by Herbert Xu

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

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 <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

2016-09-07 13:14:34

by PrasannaKumar Muralidharan

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

> 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

2016-09-07 13:17:19

by Herbert Xu

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

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 <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt