linux-kernel - [PATCH 4/7] nvmem: meson-mx-efuse: allow reading data smaller than word

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Message-Id: <20190818093345.29647-5-srinivas.kandagatla@linaro.org>
Date:   Sun, 18 Aug 2019 10:33:42 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: [PATCH 4/7] nvmem: meson-mx-efuse: allow reading data smaller than word_size

From: Martin Blumenstingl <martin.blumenstingl@...glemail.com>

Some Amlogic boards store the Ethernet MAC address inside the eFuse. The
Ethernet MAC address uses 6 bytes. The existing logic in
meson_mx_efuse_read() would write beyond the end of the data buffer when
trying to read data with a size that is not aligned to word_size (4
bytes on Meson8, Meson8b and Meson8m2).

Calculate the remaining data to copy inside meson_mx_efuse_read() so
reading 6 bytes doesn't write beyond the end of the data buffer.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Reviewed-by: Neil Armstrong <narmstrong@...libre.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
---
 drivers/nvmem/meson-mx-efuse.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvmem/meson-mx-efuse.c b/drivers/nvmem/meson-mx-efuse.c
index b9f9ce089de9..07c9f38c1c60 100644
--- a/drivers/nvmem/meson-mx-efuse.c
+++ b/drivers/nvmem/meson-mx-efuse.c
@@ -155,7 +155,8 @@ static int meson_mx_efuse_read(void *context, unsigned int offset,
 		if (err)
 			break;
 
-		memcpy(buf + i, &tmp, efuse->config.word_size);
+		memcpy(buf + i, &tmp,
+		       min_t(size_t, bytes - i, efuse->config.word_size));
 	}
 
 	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
-- 
2.21.0