The SMCCC_RET_TRNG_NO_ENTROPY switch arm is never used because the
NO_ENTROPY return value is negative and negative values are handled
above the switch by immediately returning.

Fix by handling errors using a default arm in the switch.

Fixes: 0888d04b47a1 ("hwrng: Add Arm SMCCC TRNG based driver")
Signed-off-by: James Cowgill <james.cowgill@blaize.com>
---
 drivers/char/hw_random/arm_smccc_trng.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/hw_random/arm_smccc_trng.c b/drivers/char/hw_random/arm_smccc_trng.c
index b24ac39a903b..e34c3ea692b6 100644
--- a/drivers/char/hw_random/arm_smccc_trng.c
+++ b/drivers/char/hw_random/arm_smccc_trng.c
@@ -66,33 +66,33 @@ static int smccc_trng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 	unsigned int copied = 0;
 	int tries = 0;
 
 	while (copied < max) {
 		size_t bits = min_t(size_t, (max - copied) * BITS_PER_BYTE,
 				  MAX_BITS_PER_CALL);
 
 		arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND, bits, &res);
-		if ((int)res.a0 < 0)
-			return (int)res.a0;
 
 		switch ((int)res.a0) {
 		case SMCCC_RET_SUCCESS:
 			copied += copy_from_registers(buf + copied, &res,
 						      bits / BITS_PER_BYTE);
 			tries = 0;
 			break;
 		case SMCCC_RET_TRNG_NO_ENTROPY:
 			if (!wait)
 				return copied;
 			tries++;
 			if (tries >= SMCCC_TRNG_MAX_TRIES)
 				return copied;
 			cond_resched();
 			break;
+		default:
+			return -EIO;
 		}
 	}
 
 	return copied;
 }
 
 static int smccc_trng_probe(struct platform_device *pdev)
 {
-- 
2.36.1

On Mon, Aug 01, 2022 at 08:04:18PM +0000, James Cowgill wrote:
> The SMCCC_RET_TRNG_NO_ENTROPY switch arm is never used because the
> NO_ENTROPY return value is negative and negative values are handled
> above the switch by immediately returning.
> 
> Fix by handling errors using a default arm in the switch.
> 
> Fixes: 0888d04b47a1 ("hwrng: Add Arm SMCCC TRNG based driver")
> Signed-off-by: James Cowgill <james.cowgill@blaize.com>
> ---
>  drivers/char/hw_random/arm_smccc_trng.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

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