commit 8006aff15516a170640239c5a8e6696c0ba18d8e upstream.
According to the review by Bill Cox [1], the Atmel SHA204A random number generator produces random numbers with very low entropy.
Set the lowest possible entropy for this chip just to be safe.
[1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html
Fixes: da001fb651b00e1d ("crypto: atmel-i2c - add support for SHA204A random number generator") Cc: stable@vger.kernel.org Signed-off-by: Marek Behún kabel@kernel.org Acked-by: Ard Biesheuvel ardb@kernel.org Reviewed-by: Linus Walleij linus.walleij@linaro.org Signed-off-by: Herbert Xu herbert@gondor.apana.org.au [ rebased for 5.4 ] Signed-off-by: Marek Behún kabel@kernel.org --- drivers/crypto/atmel-sha204a.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/crypto/atmel-sha204a.c b/drivers/crypto/atmel-sha204a.c index c96c14e7dab1..0ef92109ce22 100644 --- a/drivers/crypto/atmel-sha204a.c +++ b/drivers/crypto/atmel-sha204a.c @@ -107,7 +107,12 @@ static int atmel_sha204a_probe(struct i2c_client *client,
i2c_priv->hwrng.name = dev_name(&client->dev); i2c_priv->hwrng.read = atmel_sha204a_rng_read; - i2c_priv->hwrng.quality = 1024; + + /* + * According to review by Bill Cox [1], this HWRNG has very low entropy. + * [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html + */ + i2c_priv->hwrng.quality = 1;
ret = devm_hwrng_register(&client->dev, &i2c_priv->hwrng); if (ret)