Commit 25cf7f06 authored by Łukasz Stelmach's avatar Łukasz Stelmach Committed by Herbert Xu

crypto: exynos - Introduce mutex to prevent concurrent access to hardware

Hardware operations like reading random numbers and setting a seed need
to be conducted in a single thread. Therefore a mutex is required to
prevent multiple threads (processes) from accessing the hardware at the
same time.

The sequence of mutex_lock() and mutex_unlock() in the exynos_rng_reseed()
function enables switching between different threads waiting for the
driver to generate random numbers for them.
Signed-off-by: default avatarŁukasz Stelmach <l.stelmach@samsung.com>
Reviewed-by: default avatarKrzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 99c9acfe
......@@ -22,6 +22,7 @@
#include <linux/err.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
......@@ -79,6 +80,7 @@ struct exynos_rng_dev {
enum exynos_prng_type type;
void __iomem *mem;
struct clk *clk;
struct mutex lock;
/* Generated numbers stored for seeding during resume */
u8 seed_save[EXYNOS_RNG_SEED_SIZE];
unsigned int seed_save_len;
......@@ -191,6 +193,10 @@ static void exynos_rng_reseed(struct exynos_rng_dev *rng)
return;
exynos_rng_set_seed(rng, seed, read);
/* Let others do some of their job. */
mutex_unlock(&rng->lock);
mutex_lock(&rng->lock);
}
static int exynos_rng_generate(struct crypto_rng *tfm,
......@@ -206,6 +212,7 @@ static int exynos_rng_generate(struct crypto_rng *tfm,
if (ret)
return ret;
mutex_lock(&rng->lock);
do {
ret = exynos_rng_get_random(rng, dst, dlen, &read);
if (ret)
......@@ -216,6 +223,7 @@ static int exynos_rng_generate(struct crypto_rng *tfm,
exynos_rng_reseed(rng);
} while (dlen > 0);
mutex_unlock(&rng->lock);
clk_disable_unprepare(rng->clk);
......@@ -233,7 +241,9 @@ static int exynos_rng_seed(struct crypto_rng *tfm, const u8 *seed,
if (ret)
return ret;
mutex_lock(&rng->lock);
ret = exynos_rng_set_seed(ctx->rng, seed, slen);
mutex_unlock(&rng->lock);
clk_disable_unprepare(rng->clk);
......@@ -278,6 +288,8 @@ static int exynos_rng_probe(struct platform_device *pdev)
rng->type = (enum exynos_prng_type)of_device_get_match_data(&pdev->dev);
mutex_init(&rng->lock);
rng->dev = &pdev->dev;
rng->clk = devm_clk_get(&pdev->dev, "secss");
if (IS_ERR(rng->clk)) {
......@@ -328,9 +340,14 @@ static int __maybe_unused exynos_rng_suspend(struct device *dev)
if (ret)
return ret;
mutex_lock(&rng->lock);
/* Get new random numbers and store them for seeding on resume. */
exynos_rng_get_random(rng, rng->seed_save, sizeof(rng->seed_save),
&(rng->seed_save_len));
mutex_unlock(&rng->lock);
dev_dbg(rng->dev, "Stored %u bytes for seeding on system resume\n",
rng->seed_save_len);
......@@ -353,8 +370,12 @@ static int __maybe_unused exynos_rng_resume(struct device *dev)
if (ret)
return ret;
mutex_lock(&rng->lock);
ret = exynos_rng_set_seed(rng, rng->seed_save, rng->seed_save_len);
mutex_unlock(&rng->lock);
clk_disable_unprepare(rng->clk);
return ret;
......
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