ASoC: cros_ec_codec: allocate shash_desc dynamically

The wov_hotword_model_put() function has multiple large variables on
its stack, the largest of which is the result of SHASH_DESC_ON_STACK().
In total, this exceeds the warning limit for 32-bit architectures:

sound/soc/codecs/cros_ec_codec.c:776:12: error: stack frame size of 1152 bytes in function 'wov_hotword_model_put' [-Werror,-Wframe-larger-than=]

The function already has a dynamic crypto_alloc_shash() allocation, so
using kmalloc() for the descriptor is correct as well and does not
introduce any additional failure scenarios. With this, the stack usage
of wov_hotword_model_put() gets reduced to 480 bytes in my test
configuration.

Fixes: b6bc07d4360d ("ASoC: cros_ec_codec: support WoV")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20200507213405.1869430-1-arnd@arndb.de
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/sound/soc/codecs/cros_ec_codec.c b/sound/soc/codecs/cros_ec_codec.c
index d3dc42a..1948bc6 100644 (file)
--- a/sound/soc/codecs/cros_ec_codec.c
+++ b/sound/soc/codecs/cros_ec_codec.c
@@ -108,22 +108,23 @@ static int calculate_sha256(struct cros_ec_codec_priv *priv,
                            uint8_t *buf, uint32_t size, uint8_t *digest)
 {
        struct crypto_shash *tfm;
+       struct shash_desc *desc;
 
        tfm = crypto_alloc_shash("sha256", CRYPTO_ALG_TYPE_SHASH, 0);
        if (IS_ERR(tfm)) {
                dev_err(priv->dev, "can't alloc shash\n");
                return PTR_ERR(tfm);
        }
-
-       {
-               SHASH_DESC_ON_STACK(desc, tfm);
-
-               desc->tfm = tfm;
-
-               crypto_shash_digest(desc, buf, size, digest);
-               shash_desc_zero(desc);
+       desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
+       if (!desc) {
+               crypto_free_shash(tfm);
+               return -ENOMEM;
        }
+       desc->tfm = tfm;
+       crypto_shash_digest(desc, buf, size, digest);
+       shash_desc_zero(desc);
 
+       kfree(desc);
        crypto_free_shash(tfm);
 
 #ifdef DEBUG