linux-kernel - [PATCH 5.15 055/132] crypto: qcom-rng - fix infinite loop on requests not multiple of WORD

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Date:   Mon, 23 May 2022 19:04:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ondrej Mosnacek <omosnace@...hat.com>,
        Brian Masney <bmasney@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 5.15 055/132] crypto: qcom-rng - fix infinite loop on requests not multiple of WORD_SZ

From: Ondrej Mosnacek <omosnace@...hat.com>

commit 16287397ec5c08aa58db6acf7dbc55470d78087d upstream.

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>
Reviewed-by: Brian Masney <bmasney@...hat.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/crypto/qcom-rng.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/crypto/qcom-rng.c
+++ b/drivers/crypto/qcom-rng.c
@@ -65,6 +65,7 @@ static int qcom_rng_read(struct qcom_rng
 		} else {
 			/* copy only remaining bytes */
 			memcpy(data, &val, max - currsize);
+			break;
 		}
 	} while (currsize < max);