[PATCH v2] hwrng: core - Allocate memory during module init

[PATCH v2] 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.

Change in v2:
Fix memory leak when register_miscdev fails.

Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
---
 drivers/char/hw_random/core.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 9203f2d..4827945 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) {
@@ -573,7 +557,26 @@ EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
 
 static int __init hwrng_modinit(void)
 {
-	return register_miscdev();
+	int ret = -ENOMEM;
+
+	/* 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;
+	}
+
+	ret = register_miscdev();
+	if (ret) {
+		kfree(rng_fillbuf);
+		kfree(rng_buffer);
+	}
+
+	return ret;
 }
 
 static void __exit hwrng_modexit(void)
-- 
2.5.0

Re: [PATCH v2] hwrng: core - Allocate memory during module init

[Herbert Xu]

On Wed, Sep 07, 2016 at 08:18:02PM +0530, PrasannaKumar Muralidharan wrote:
> 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.
> 
> Change in v2:
> Fix memory leak when register_miscdev fails.
> 
> Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>

Patch applied.  Thanks.
-- 
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