2022-08-01 20:28:05

by James Cowgill

[permalink] [raw]
Subject: [PATCH] hwrng: arm-smccc-trng - fix NO_ENTROPY handling

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 <[email protected]>
---
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