[PATCH v2] nvmem: meson-mx-efuse: allow reading data smaller than word_size

[PATCH v2] nvmem: meson-mx-efuse: allow reading data smaller than word_size

[Martin Blumenstingl]

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@googlemail.com>
---
Changes since v1:
- switch from min() to min_t() to get rid of a compiler warning


 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 2976aef87c82..e8fc0baa09e7 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,
-- 
2.22.0

Re: [PATCH v2] nvmem: meson-mx-efuse: allow reading data smaller than word_size

[Neil Armstrong]

On 27/07/2019 21:34, Martin Blumenstingl wrote:
> 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@googlemail.com>
> ---
> Changes since v1:
> - switch from min() to min_t() to get rid of a compiler warning
> 
> 
>  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 2976aef87c82..e8fc0baa09e7 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,
> 

Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>

Re: [PATCH v2] nvmem: meson-mx-efuse: allow reading data smaller than word_size

[Srinivas Kandagatla]

On 27/07/2019 20:34, Martin Blumenstingl wrote:
> 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@googlemail.com>
> ---

Applied Thanks,
Srini