linux-kernel - [PATCH] crypto: qcom-rng - fix infinite loop on requests not multiple of WORD

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Message-Id: <20220503115010.1750296-1-omosnace@redhat.com>
Date:   Tue,  3 May 2022 13:50:10 +0200
From:   Ondrej Mosnacek <omosnace@...hat.com>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Brian Masney <bmasney@...hat.com>,
        linux-arm-msm@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH] crypto: qcom-rng - fix infinite loop on requests not multiple of WORD_SZ

The commit referenced in the Fixes tag removed the 'break' from the else
branch in qcom_rng_read(), causing an infinite loop whenever 'max' is
not a multiple of WORD_SZ. This can be reproduced e.g. by running:

    kcapi-rng -b 67 >/dev/null

There are many ways to fix this without adding back the 'break', but
they all seem more awkward than simply adding it back, so do just that.

Tested on a machine with Qualcomm Amberwing processor.

Fixes: a680b1832ced ("crypto: qcom-rng - ensure buffer for generate is completely filled")
Cc: stable@...r.kernel.org
Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
---
 drivers/crypto/qcom-rng.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/crypto/qcom-rng.c b/drivers/crypto/qcom-rng.c
index 11f30fd48c141..031b5f701a0a3 100644
--- a/drivers/crypto/qcom-rng.c
+++ b/drivers/crypto/qcom-rng.c
@@ -65,6 +65,7 @@ static int qcom_rng_read(struct qcom_rng *rng, u8 *data, unsigned int max)
 		} else {
 			/* copy only remaining bytes */
 			memcpy(data, &val, max - currsize);
+			break;
 		}
 	} while (currsize < max);
 
-- 
2.35.1