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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, James Cowgill <james.cowgill@blaize.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.19 509/717] hwrng: arm-smccc-trng - fix NO_ENTROPY handling
Date:   Sat, 22 Oct 2022 09:26:28 +0200
Message-Id: <20221022072520.767107550@linuxfoundation.org>
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From: James Cowgill <james.cowgill@blaize.com>

[ Upstream commit 042b4b169c6fb9d4df268d66282d7302dd73d37b ]

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>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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
@@ -71,8 +71,6 @@ static int smccc_trng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 				  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:
@@ -88,6 +86,8 @@ static int smccc_trng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 				return copied;
 			cond_resched();
 			break;
+		default:
+			return -EIO;
 		}
 	}
 
-- 
2.35.1